Selection of Detection Methods for Hepatobiliary Metabolism-Related Indicators

Detection of hepatobiliary metabolism-related indicators is used to evaluate hepatocyte synthesis and transport, bile formation, biliary excretion, cholestasis, cholesterol homeostasis, and bile discharge function from the perspectives of bile acids, bilirubin, cholesterol, cholesterol esters, lipoprotein transport, hepatic lipid processing, and gallbladder functional regulation.

Keywords: hepatobiliary metabolism; bile acid detection; bilirubin detection; cholesterol detection; cholesterol ester; hepatic lipase; urinary bilirubin; urobilinogen

1 Indicator Framework for Hepatobiliary Metabolism Detection

1.1 Bile Acid-Related Indicators

(1) Total bile acids

Total bile acids (TBA) reflect the overall bile acid level in a sample and are suitable for preliminary evaluation of cholestasis, abnormal hepatobiliary excretion, and changes in bile acid synthesis or transport. Serum, plasma, bile, liver tissue, intestinal contents, and cell models can all be selected for TBA detection according to the experimental objective. However, absolute values from different sample types should not be directly compared; interpretation should take dilution factor, normalization method, and sampling site into account.

(2) Bile acid components

Cholic acid, chenodeoxycholic acid, deoxycholic acid, ursodeoxycholic acid, lithocholic acid, and their glycine- or taurine-conjugated derivatives together constitute the bile acid profile. An increase in total bile acids only indicates an overall change in bile acid levels and cannot determine whether the proportions of primary bile acids, secondary bile acids, or conjugated bile acids have changed. For studies involving bile acid synthesis, enterohepatic circulation, and gut microbiota-mediated metabolism, component analysis using HPLC, UPLC, or LC-MS/MS should be performed.

1.2 Bilirubin and Bile Pigment Excretion Indicators

(1) Total bilirubin and direct bilirubin

Total bilirubin (TBIL) reflects the overall bilirubin level, while direct bilirubin (DBIL) is more closely associated with conjugated bilirubin and bile excretion-related changes. Hepatocellular injury, cholestasis, biliary obstruction, and abnormal bile pigment excretion may all lead to changes in bilirubin indicators. Therefore, TBIL and DBIL are more suitable as supporting indicators for evaluating hepatobiliary excretory status and should not be used alone to explain all changes in hepatobiliary metabolism.

(2) Urinary bilirubin and urobilinogen

Urinary bilirubin and urobilinogen are auxiliary urinary indicators related to bile pigment metabolism. Positive urinary bilirubin often suggests that conjugated bilirubin has entered the urine, whereas changes in urobilinogen are associated with bilirubin enterohepatic circulation, hepatocellular processing capacity, and biliary excretion status. These two indicators are suitable for auxiliary screening of hepatobiliary excretory abnormalities, but should be interpreted together with serum bilirubin, bile acids, and the background of the experimental model.

1.3 Cholesterol and Biliary Lipid Indicators

(1) Total cholesterol and free cholesterol

Cholesterol is an important component of biliary lipids. The ratio of cholesterol, bile acids, and phospholipids in bile affects cholesterol solubility and crystallization risk. Total cholesterol (TC) is suitable for evaluating overall cholesterol levels, whereas free cholesterol (FC) is more appropriate for analyzing cholesterol crystallization, gallstone formation, and biliary lipid stability.

(2) Cholesterol esters

Cholesterol esters (CE) are commonly used to evaluate cholesterol storage, transport, and esterification status. Cholesterol ester detection in liquid samples is suitable for serum, plasma, or bile-related systems, whereas cholesterol ester detection in tissues and cells is more suitable for liver tissue, gallbladder tissue, macrophages, hepatocytes, or cholesterol metabolism models. CE results usually need to be interpreted together with TC, FC, and lipoprotein indicators.

1.4 Hepatobiliary Regulatory and Functional Indicators

(1) Cholesterol transport and bile acid synthesis

CYP7A1 participates in the rate-limiting step of cholesterol conversion into bile acids, NPC1L1 is associated with cholesterol absorption, and LCAT is involved in cholesterol esterification and lipoprotein metabolism. These indicators are not equivalent to direct measurements of bile acid or cholesterol content, but they can be used to explain regulatory mechanisms related to cholesterol homeostasis, bile acid synthesis, and enterohepatic circulation.

(2) Hepatic lipid transport and lipase activity

Hepatic lipase (HL) participates in the hydrolysis of lipoproteins and triglycerides, while liver-type fatty acid-binding protein (FABP1/LFABP) is associated with hepatocellular fatty acid transport, lipid metabolism, and hepatocellular injury. These indicators are suitable as mechanistic supplements for assessing hepatic lipid processing capacity and hepatocellular metabolic status, but should not replace content measurements such as TC, FC, CE, or TBA.

(3) Gallbladder contraction and bile secretion regulation

Cholecystokinin (CCK) and its receptor are associated with gallbladder contraction, bile discharge, and digestion. In studies of gallbladder function, bile excretion dynamics, or cholestasis, CCK or CCKAR can be used as functional regulatory indicators. However, their results should be analyzed together with bile acids, bilirubin, and bile flow.

Table 1 Hepatobiliary Metabolism-Related Indicators and Detection Positioning

Indicator Category	Representative Indicators	Recommended Methods	Main Samples	Application Positioning
Total bile acids	TBA	Enzymatic assay, microassay, colorimetric assay	Serum, plasma, bile, tissue, cells	Evaluation of cholestasis, bile acid metabolism, and hepatobiliary excretion
Bile acid components	CA, CDCA, DCA, LCA, UDCA, and conjugated bile acids	HPLC, UPLC, LC-MS/MS	Bile, serum, feces, tissue	Bile acid profiling, enterohepatic circulation, and gut microbiota metabolism studies
Bilirubin metabolism	TBIL, DBIL, urinary bilirubin, urobilinogen	Colorimetric assay, qualitative chromogenic assay, microassay	Serum, urine, bile, tissue	Evaluation of bile pigment metabolism, cholestasis, and biliary excretion
Cholesterol metabolism	TC, FC, CE	COD-PAP method, colorimetric assay, fluorescence assay	Serum, bile, tissue, cells	Biliary lipid composition, gallstone risk, and cholesterol homeostasis
Lipoprotein cholesterol	LDL-C, HDL-C	COD-PAP method, colorimetric assay	Serum, plasma	Auxiliary evaluation of hepatic lipid transport and blood lipid metabolism
Hepatic lipid processing	HL, FABP1/LFABP	Activity assay, ELISA	Serum, tissue, cells	Auxiliary evaluation of hepatic lipid hydrolysis, fatty acid transport, and hepatocellular injury
Regulatory factors	CYP7A1, NPC1L1, LCAT, CCK, CCKAR	ELISA, immunoassay, molecular detection	Serum, tissue, cells	Mechanistic studies of bile acid synthesis, cholesterol transport, and gallbladder function

2 Selection of Detection Methods

2.1 Enzymatic and Colorimetric Assays

(1) Method positioning

Enzymatic and colorimetric assays are suitable for routine content detection of total bile acids, bilirubin, cholesterol, free cholesterol, cholesterol esters, and related indicators. These methods are relatively standardized and suitable for multi-sample comparison and model screening. However, they are sensitive to sample color, turbidity, lipid background, and dilution factor. Sample blanks are particularly important for bile, tissue homogenates, and hyperlipidemic samples.

(2) Scope of application

Enzymatic and colorimetric assays can be used for total-level evaluation, but they do not provide molecular component information. Increased total bile acids, cholesterol, or bilirubin only indicates that a certain indicator category has changed; it cannot directly identify specific bile acid components, bilirubin conjugation status, or lipid profile structure. Therefore, mechanistic studies often require combined analysis with LC-MS/MS, HPLC, or immunoassays.

2.2 Microassays and High-Throughput Detection

(1) Method positioning

Microassays are suitable for experiments with limited sample volume or multi-well plate-based batch detection, such as mouse serum, micro-volume bile samples, tissue homogenates, cell lysates, and culture supernatants. This approach reduces sample consumption and improves detection throughput, but it requires higher precision in pipetting, inter-well consistency, and standard curve quality.

(2) Quality control

In microassays, the standard curve, sample dilution, replicate consistency, and blank subtraction are critical for reliable results. Bile samples, lipid-rich samples, and deeply colored samples should first undergo pilot testing to confirm that diluted readings fall within the linear range before formal batch detection.

2.3 Qualitative Chromogenic Assays

(1) Method positioning

Urinary bilirubin and urobilinogen are commonly detected using qualitative or semi-quantitative chromogenic assays, which serve as auxiliary indicators for bile pigment metabolism and hepatobiliary excretory abnormalities. Qualitative urinary bilirubin detection reflects the excretion of conjugated bilirubin into urine, while urobilinogen detection is associated with bilirubin enterohepatic circulation and hepatocellular processing capacity.

(2) Scope of application

Qualitative urine testing is suitable for screening and trend evaluation, but should not replace serum bilirubin, total bile acid, or bile acid profiling analysis. Urine concentration, sampling time, storage conditions, and drug interference may all affect results; therefore, findings should be interpreted together with blood indicators, tissue indicators, or the experimental model background.

2.4 Activity Assays and ELISA

(1) Enzyme activity assays

Hepatic lipase or hepatic esterase activity assays are suitable for evaluating hepatic lipid hydrolysis and lipoprotein metabolism. These methods detect changes in enzyme function and are not equivalent to content measurements of cholesterol, cholesterol esters, or lipoprotein cholesterol. When used in lipid metabolism studies, they should be analyzed together with TC, FC, CE, LDL-C, and HDL-C.

(2) ELISA detection

ELISA is suitable for detecting protein or peptide regulatory factors such as LCAT, CYP7A1, NPC1L1, CCK, CCKAR, BLVRB, and FABP1/LFABP, and is used to explain changes in hepatobiliary metabolic pathways. These indicators are more mechanistically oriented and cannot directly replace content detection of TBA, TBIL, DBIL, or TC.

2.5 HPLC, UPLC, and LC-MS/MS

(1) Method positioning

HPLC, UPLC, and LC-MS/MS are suitable for bile acid profiling, lipid profiling, and complex metabolite component analysis. LC-MS/MS can simultaneously detect multiple free, glycine-conjugated, and taurine-conjugated bile acids, and can further resolve bile acid synthesis, conversion, and enterohepatic circulation patterns.

(2) Scope of application

Chromatographic and mass spectrometric methods provide high information content, but they require higher standards for reference materials, internal standards, sample pretreatment, instrumental conditions, and data analysis. If the experimental objective is only large-sample total-level screening, enzymatic or colorimetric assays are more efficient. If the objective is to interpret metabolic pathways and component remodeling, LC-MS/MS should be prioritized.

Table 2 Comparison of Common Detection Methods for Hepatobiliary Metabolism Indicators

Method Type	Applicable Indicators	Main Advantages	Main Limitations	Suitable Scenarios
Enzymatic/colorimetric assay	TBA, TBIL, DBIL, TC, FC, CE	Standardized operation; suitable for routine content detection	Affected by color, turbidity, and matrix effects	Multi-sample screening, model comparison, routine detection
Microassay	TBA, TBIL, DBIL, TC, FC, CE, HL	Low sample consumption; suitable for high-throughput detection	Requires high pipetting accuracy and validated linear range	Small-volume samples, animal experiments, cell models
Qualitative chromogenic assay	Urinary bilirubin, urobilinogen	Simple operation; suitable for auxiliary screening	Limited quantitative capability	Urinary bile pigment metabolism evaluation
Activity assay	HL and other metabolic enzymes	Directly reflects enzyme functional status	Does not represent total substrate or product levels	Hepatic lipid metabolism and enzyme function studies
ELISA	LCAT, CYP7A1, NPC1L1, CCK, FABP1, etc.	Suitable for protein and regulatory factor detection	Does not represent metabolite content	Mechanistic studies and pathway regulation analysis
HPLC/UPLC	Bile acids, cholesterol, selected lipid components	Enables component separation	Identification and sensitivity depend on detector performance	Component analysis and method development
LC-MS/MS	Bile acid profile, lipidome, metabolome	Strong component-resolving capability	Requires instrumentation and internal standards	Bile acid metabolomics and enterohepatic circulation studies

3 Detection Design for Different Sample Types

3.1 Serum and Plasma Samples

(1) Detection indicators

Serum and plasma are suitable for detecting TBA, TBIL, DBIL, TC, FC, CE, LDL-C, HDL-C, HL, and selected ELISA indicators. These measurements can be used to evaluate hepatobiliary excretion, bile pigment metabolism, blood lipid transport, lipoprotein hydrolysis, and cholesterol homeostasis. Blood collection status, postprandial timing, hemolysis, lipemia, anticoagulant system, and freeze-thaw cycles all affect result consistency.

(2) Method selection

Routine content indicators can be detected using microassays, colorimetric assays, or the COD-PAP method. Enzyme activity indicators can be measured using activity assay kits, protein regulatory indicators can be detected using ELISA, and bile acid profiling or lipid profiling should be performed by LC-MS/MS. In batch experiments, sample collection time, processing time, and storage conditions should be standardized to reduce non-experimental variation.

3.2 Urine Samples

(1) Detection indicators

Urine samples are more suitable for auxiliary detection of bile pigment metabolism, such as urinary bilirubin and urobilinogen. Positive urinary bilirubin is often associated with abnormal excretion of conjugated bilirubin, whereas changes in urobilinogen can reflect alterations in bilirubin enterohepatic circulation and hepatocellular processing capacity.

(2) Result interpretation

Urine test results are strongly affected by urine concentration, sampling time, storage conditions, and drug interference. Abnormal urinary bilirubin or urobilinogen should not be interpreted alone as evidence of a specific hepatobiliary disease or mechanistic change, but should be evaluated together with serum TBIL, DBIL, TBA, and the model background.

3.3 Bile Samples

(1) Detection indicators

Bile samples can be used to detect total bile acids, bilirubin, cholesterol, free cholesterol, cholesterol esters, and bile acid profiles. Target analyte concentrations in bile are usually high, and bile often has deep color, high viscosity, and abundant lipid and mucus components. Therefore, dilution, clarification, and sample blank correction require particular attention before detection.

(2) Method selection

Total-level screening can be performed using TBA, TBIL, TC, FC, and CE assay kits. Analysis of bile acid components, cholesterol metabolites, or lipid profiles should be conducted using HPLC, UPLC, or LC-MS/MS. Before formal bile sample detection, dilution linearity should be verified to avoid readings outside the standard curve range.

3.4 Tissue and Cell Samples

(1) Tissue samples

Liver tissue, gallbladder tissue, intestinal tissue, and biliary tract-related tissues can be used to detect bile acids, cholesterol, cholesterol esters, hepatic lipase activity, and regulatory proteins. Tissue sampling site, wet weight, homogenization ratio, and centrifugation conditions should be standardized. Results can be normalized to tissue weight, protein amount, or cell number.

(2) Cell samples

Hepatocytes, intestinal epithelial cells, cholangiocytes, macrophages, or cholesterol metabolism models can be used to assess intracellular cholesterol, cholesterol esters, bile acid processing capacity, and related protein expression. Cell experiments should include treatment blanks, lysis buffer blanks, and protein normalization to avoid bias caused by differences in cell number.

Table 3 Indicator Combinations for Different Sample Types

Sample Type	Recommended Indicators	Recommended Methods	Result Expression
Serum/plasma	TBA, TBIL, DBIL, TC, FC, CE, LDL-C, HDL-C, HL	Microassay, colorimetric assay, COD-PAP method, activity assay, ELISA	Concentration, enzyme activity, or relative intergroup change
Urine	Urinary bilirubin, urobilinogen	Harrison method, modified Ehrlich method	Qualitative or semi-quantitative results
Bile	TBA, TBIL, TC, FC, CE, bile acid profile	Enzymatic assay, colorimetric assay, HPLC, LC-MS/MS	Concentration after dilution correction
Liver tissue	TBA, TC, FC, CE, HL, CYP7A1, FABP1/LFABP, BLVRB	Microassay, activity assay, ELISA, LC-MS/MS	Normalized to wet weight or protein amount
Intestinal tissue/intestinal cells	NPC1L1, bile acid-related indicators, cholesterol-related indicators	ELISA, microassay, LC-MS/MS	Normalized to tissue weight, protein amount, or cell number
Gallbladder-related samples	CCK, CCKAR, biliary lipid indicators	ELISA, colorimetric assay, microassay	Correlation analysis with gallbladder function or bile discharge status

4 Indicator Combinations in Application Scenarios

4.1 Cholestasis and Abnormal Biliary Excretion

(1) Basic combination

Studies of cholestasis or abnormal biliary excretion should prioritize TBA, TBIL, and DBIL detection, with bile samples or liver tissue indicators added according to the sample source. Increased TBA may indicate bile acid accumulation, while increased DBIL is more suggestive of abnormal conjugated bilirubin excretion. Their combined use is more informative than either indicator alone for assessing hepatobiliary excretory status.

(2) Mechanistic extension

If changes in bile acid synthesis and transport need to be explained, CYP7A1, bile acid profiling, or related transporter detection can be added. TBA elevation alone cannot distinguish increased bile acid synthesis, impaired transport, excretory obstruction, or altered enterohepatic circulation. Component analysis or mechanistic indicators should be selected according to the experimental model.

4.2 Bilirubin Metabolism and Jaundice-Related Studies

(1) Basic combination

Bilirubin metabolism studies can use a combination of TBIL, DBIL, urinary bilirubin, and urobilinogen. TBIL and DBIL are used to evaluate bilirubin burden in blood or bile, while urinary bilirubin and urobilinogen serve as auxiliary indicators related to bile pigment excretion and enterohepatic circulation.

(2) Mechanistic extension

Biliverdin/bilirubin metabolism-related proteins such as BLVRB can be used as mechanistic indicators to analyze bile pigment reduction, redox status, and bilirubin metabolic regulation. These indicators do not replace TBIL or DBIL content measurements and are more suitable for explaining changes in bile pigment metabolic pathways.

4.3 Cholesterol Metabolism and Gallstone-Related Studies

(1) Basic combination

Studies of gallstones and biliary lipid composition should not rely solely on total cholesterol detection, but should simultaneously evaluate TC, FC, CE, and bile acid levels. Cholesterol crystallization risk is associated with the ratio of cholesterol, bile acids, and phospholipids; elevated TC alone cannot fully explain changes in biliary micellar stability.

(2) Mechanistic extension

LCAT, NPC1L1, CYP7A1, and HL can be used as mechanistic indicators related to cholesterol esterification, cholesterol absorption, bile acid synthesis, and lipoprotein hydrolysis. If the research objective involves hepato-intestinal cholesterol flux, blood lipid indicators, tissue cholesterol esters, hepatic lipase activity, and bile acid components should be analyzed together.

4.4 Hepatic Lipid Transport and Hepatocellular Injury-Related Studies

(1) Lipid transport

FABP1/LFABP can be used to evaluate changes related to hepatocellular fatty acid binding and transport. It is suitable for fatty liver, abnormal cholesterol metabolism, drug-induced liver injury, and hepatocellular lipid loading models. This indicator is better used as an auxiliary marker of hepatic lipid metabolism and liver injury, and should be combined with TC, FC, CE, LDL-C, HDL-C, or tissue lipid detection.

(2) Sample processing

When detecting hepatic lipase activity, FABP1/LFABP, or other protein indicators in liver tissue or cell samples, protein extraction efficiency, lysis system, centrifugation-based clarification, and protein normalization should be carefully controlled. If the same experiment includes both metabolite content detection and protein indicator detection, compatible extraction systems should be used separately to avoid forcing one pretreatment method to serve all detection purposes.

4.5 Gallbladder Function and Regulation of Bile Discharge

(1) Basic combination

Gallbladder function studies can combine CCK and CCKAR with bile flow, bile acids, bilirubin, and biliary lipid indicators. Changes in CCK or CCKAR suggest that gallbladder contraction and bile discharge regulation may be altered, but they do not independently represent changes in bile composition.

(2) Sample design

Gallbladder-related studies should distinguish serum hormone levels, receptor expression in gallbladder tissue, and changes in bile composition whenever possible. If CCK, bile acids, and biliary lipids are included in the same experiment, their respective meanings should be clearly defined: regulatory signal, bile acid metabolism, and bile composition. They should not be treated as indicators of the same category.

Table 4 Recommended Indicator Combinations in Hepatobiliary Metabolism Studies

Research Direction	Core Indicators	Extended Indicators	Method Combination
Cholestasis	TBA, TBIL, DBIL	Bile acid profile, CYP7A1	Microassay/colorimetric assay + LC-MS/MS/ELISA
Jaundice and bilirubin metabolism	TBIL, DBIL, urinary bilirubin, urobilinogen	BLVRB	Microassay + qualitative chromogenic assay + ELISA
Gallstones and biliary lipids	TC, FC, CE, TBA	Bile acid profile, LCAT	COD-PAP method/microassay + LC-MS/MS/ELISA
Cholesterol absorption and transport	TC, FC, CE, LDL-C, HDL-C	NPC1L1, LCAT, HL	Colorimetric assay + COD-PAP method + ELISA/activity assay
Hepatic lipid metabolism	TC, FC, CE, HL	FABP1/LFABP	Microassay + activity assay + ELISA
Gallbladder function	CCK, CCKAR	Bile acids, bilirubin, bile flow	ELISA + content detection
Enterohepatic circulation	TBA, bile acid profile, urobilinogen	NPC1L1, CYP7A1	Microassay + LC-MS/MS + ELISA

5 Result Interpretation and Quality Control

5.1 Standard Curve and Linear Range

(1) Linear range

Content detection of TBA, TBIL, DBIL, TC, FC, CE, and related indicators should ensure that sample readings fall within the linear range of the standard curve. Bile, hyperlipidemic serum, and high-concentration tissue homogenates can easily exceed this range; suitable dilution factors should therefore be determined through pilot experiments.

(2) Dilution linearity

Dilution linearity should be verified for samples with complex matrices. If calculated results differ across dilution factors, this suggests matrix interference, insufficient background subtraction, or reaction inhibition. Dilution ratio, centrifugation/clarification, or sample blank settings should then be optimized.

5.2 Blanks and Matrix Interference

(1) Sample blanks

Sample blanks should be included for bile, tissue homogenates, lipemic samples, and colored samples. Bile itself is deeply colored and contains high levels of bilirubin and lipids. Without background subtraction, colorimetric or fluorescence assay results may be overestimated.

(2) Spike recovery

Spike recovery can be used to evaluate whether the matrix affects the detection signal. Low recovery suggests extraction loss or reaction inhibition, whereas high recovery may be associated with insufficient background subtraction or signal enhancement by interfering substances. This is particularly relevant for bile, feces, tissue homogenates, and culture medium samples.

5.3 Normalization and Intergroup Comparison

(1) Tissue and cell normalization

Tissue samples can be normalized to wet weight, protein amount, or homogenate volume, while cell samples can be normalized to protein amount, cell number, or total DNA amount. Different normalization methods affect result interpretation; therefore, the same standard should be maintained within a single experiment.

(2) Multi-indicator integrated interpretation

Hepatobiliary metabolism studies should not rely on a single indicator. Increased TBA, increased DBIL, altered TC/FC ratio, CE accumulation, altered HL activity, or abnormal CCK levels point to different layers of biological change. Only by integrating content detection, activity assays, mechanistic indicators, and sample source can hepatobiliary metabolic status be assessed more accurately.

Table 5 Common Abnormal Results and Optimization Strategies

Abnormal Finding	Possible Cause	Optimization Strategy
Excessively high TBA reading	High bile acid concentration, insufficient dilution, reading outside the linear range	Increase dilution factor and verify dilution linearity
High TBIL/DBIL background	Deep sample color, insufficient blank subtraction	Set sample blanks and optimize clarification
Large replicate variation in TC or FC	Insufficient mixing of lipid-rich samples, pipetting error	Mix thoroughly and use calibrated pipettes
Low CE result	Insufficient extraction efficiency or improper sample storage	Optimize extraction procedure and reduce freeze-thaw cycles
Abnormal variation in HL activity	Improper sample storage, reduced enzyme activity, or inconsistent reaction conditions	Standardize sampling, storage, reaction temperature, and detection time
Unstable urinary bilirubin result	Improper urine storage, light exposure, or drug interference	Use fresh samples and control storage conditions
Large batch-to-batch variation in ELISA	Differences in standard curve, incubation conditions, or plate washing	Detect key samples in the same batch and strictly standardize procedures
Low LC-MS/MS response	Ion suppression, unsuitable internal standard, extraction loss	Optimize sample pretreatment and use internal standard correction

6 Selection of Related Products and Materials

Table 6 Core Content and Activity Detection Products for Hepatobiliary Metabolism

Cat. No.	Product Name	Grade & Purity	Indicator Category	Application Positioning
T1522089	Total Bile Acids (TBA) Content Assay Kit (Micro Method)	BioReagent	Bile acid metabolism	Detection of total bile acid levels in serum, plasma, bile, tissue, or cell samples; suitable for evaluating cholestasis and bile acid metabolism
T1522116	Total Bilirubin (TBIL) Content Assay Kit (Micro Method)	BioReagent	Bilirubin metabolism	Detection of total bilirubin content; suitable for studies of bile pigment metabolism, cholestasis, and hepatobiliary excretory abnormalities
D1522115	Direct Bilirubin (DBIL) Content Assay Kit (Micro Method)	BioReagent	Bilirubin metabolism	Detection of direct/conjugated bilirubin; suitable for evaluating biliary excretion, cholestasis, and bilirubin metabolism
U1509474	Urine Bilirubin Qualitative Detection Kit (Harrison's Method)	BioReagent	Auxiliary urinary bile pigment indicator	Qualitative detection of urinary bilirubin; suitable for auxiliary screening of hepatobiliary excretory abnormalities and bilirubin metabolism-related changes
U1509467	Urobilinogen Qualitative Detection Kit (Modified Ehrlich's Method)	BioReagent	Auxiliary urinary bile pigment indicator	Qualitative detection of urobilinogen; suitable for evaluating bilirubin enterohepatic circulation and urinary auxiliary indicators
T1505557	Total Cholesterol (TC) Content Assay Kit (Single-Reagent COD-PAP, Micro Method)	BioReagent	Cholesterol metabolism	Microassay detection of total cholesterol; suitable for studies of biliary lipid composition, hepatic cholesterol metabolism, and gallstone-related mechanisms
T1505558	Total Cholesterol (TC) Content Assay Kit (Double-Reagent COD-PAP, Micro Method)	BioReagent	Cholesterol metabolism	Dual-reagent microassay for total cholesterol; suitable for batch samples and complex matrix analysis
T1515864	Total Cholesterol (TC) Content Assay Kit (Single-Reagent COD-PAP, Colorimetric Method)	BioReagent	Cholesterol metabolism	Routine colorimetric detection of total cholesterol; suitable for spectrophotometric or conventional colorimetric systems
F1505559	Free Cholesterol (FC) Content Assay Kit (COD-PAP, Micro Method)	BioReagent	Free cholesterol	Microassay detection of free cholesterol; suitable for studies of biliary lipid composition, cholesterol crystallization, and gallstone risk
F1515865	Free Cholesterol (FC) Content Assay Kit (Single Reagent COD-PAP, Colorimetric Method)	BioReagent	Free cholesterol	Single-reagent colorimetric detection of free cholesterol; suitable for routine sample analysis
F1515866	Free Cholesterol (FC) Content Assay Kit (Dual Reagent COD-PAP, Colorimetric Method)	BioReagent	Free cholesterol	Dual-reagent colorimetric detection of free cholesterol; suitable for detection systems requiring reduced background interference
C1521752	Cholesterol Ester (CE) Content Assay Kit for Liquid Samples (Micro Method)	BioReagent	Cholesterol ester	Detection of cholesterol esters in serum, plasma, bile, and other liquid samples; suitable for studies of cholesterol esterification and lipid transport
C1521753	Cholesterol Ester (CE) Content Assay Kit for Tissues/Cells (Micro Method)	BioReagent	Cholesterol ester	Detection of cholesterol esters in liver tissue, gallbladder tissue, or cell models; suitable for evaluating tissue/cellular cholesterol storage
C1373333	Total Cholesterol and Cholesteryl Ester Fluorometric Assay Kit	BioReagent, colorimetric assay, for analytical use	Total cholesterol/cholesterol ester	Combined detection of total cholesterol and cholesterol esters; suitable for cholesterol metabolism and biliary lipid composition analysis
L1505568	Low Density Lipoprotein Cholesterol (LDL-C) Content Assay Kit (COD-PAP, Micro Method)	BioReagent	Lipoprotein cholesterol	Microassay detection of LDL-C; suitable as an auxiliary indicator for hepatic cholesterol transport and blood lipid metabolism
L1515908	Low-Density Lipoprotein Cholesterol (LDL-C) Content Assay Kit (COD-PAP, Colorimetric Method)	BioReagent	Lipoprotein cholesterol	Colorimetric detection of LDL-C; suitable for auxiliary evaluation of blood lipid metabolism and hepatic lipid transport
L1505572	High Density Lipoprotein Cholesterol (HDL-C) Content Assay Kit (COD-PAP, Micro Method)	BioReagent	Lipoprotein cholesterol	Microassay detection of HDL-C; suitable for auxiliary evaluation of reverse cholesterol transport and hepatic lipid metabolism
H1515907	High-Density Lipoprotein Cholesterol (HDL-C) Content Assay Kit (COD-PAP, Colorimetric Method)	BioReagent	Lipoprotein cholesterol	Colorimetric detection of HDL-C; suitable for studies of blood lipid metabolism and cholesterol transport
H1521969	Hepatic Lipase (HL) Activity Assay Kit (Micro Method)	BioReagent	Hepatic lipase activity	Microassay detection of hepatic lipase activity; suitable for studies of hepatic lipid hydrolysis, lipoprotein metabolism, and blood lipid regulation
L1522152	Liver Esterase (HL) Activity Assay Kit (Micro Method)	BioReagent	Hepatic esterase/hepatic lipase activity	Microassay detection of hepatic esterase activity; suitable for evaluating hepatic lipid metabolism and changes in enzyme activity
L1522153	Liver Esterase (HL) Activity Assay Kit (Colorimetric Method)	BioReagent	Hepatic esterase/hepatic lipase activity	Colorimetric detection of hepatic esterase activity; suitable for conventional spectrophotometric detection systems

Table 7 Products Related to Mechanistic Studies of Hepatobiliary Metabolism

Cat. No.	Product Name	Grade & Purity	Indicator Category	Application Positioning
EJ1513909	Human Lecithin Cholesterol Acyltransferase (LCAT) ELISA Kit	BioReagent	Cholesterol esterification/lipoprotein metabolism	LCAT detection in human samples; suitable for studies of cholesterol esterification, HDL metabolism, and lipoprotein remodeling
EJ1512013	Rat Lecithin Cholesterol Acyltransferase (LCAT) ELISA Kit	BioReagent	Cholesterol esterification/lipoprotein metabolism	LCAT detection in rat models; suitable for mechanistic studies of hepatic cholesterol metabolism
EJ1512704	Mouse Lecithin Cholesterol Acyltransferase (LCAT) ELISA Kit	BioReagent	Cholesterol esterification/lipoprotein metabolism	LCAT detection in mouse models; suitable for studies of cholesterol esterification and lipoprotein metabolism
EJ1513105	Mouse Cholesterol 7 Alpha Hydroxylase (CYP7A1) ELISA Kit	BioReagent	Bile acid synthesis	CYP7A1 detection in mice; suitable for studies of cholesterol conversion to bile acids and bile acid synthesis pathways
EJ1512734	Mouse NPC1-like Intracellular Cholesterol Transporter 1 (NPC1L1) ELISA Kit	BioReagent	Cholesterol absorption/transport	NPC1L1 detection in mice; suitable for studies of intestinal cholesterol absorption and hepato-intestinal cholesterol transport
EJ1514697	Human Biliverdin Reductase B (BLVRB) ELISA Kit	BioReagent	Bile pigment metabolism	BLVRB detection in human samples; suitable for studies of biliverdin/bilirubin metabolism and redox-related mechanisms
EJ1515660	Human Cholecystokinin (CCK) ELISA Kit	BioReagent	Gallbladder function regulation	CCK detection in human samples; suitable for studies of gallbladder contraction, bile discharge, and digestive regulation
EJ1515424	Rat Cholecystokinin (CCk) ELISA Kit	BioReagent	Gallbladder function regulation	CCK detection in rat models; suitable for studies of gallbladder function and bile discharge regulation
EJ1512260	Rat Cholecystokinin A Receptor (CCKAR) ELISA Kit	BioReagent	Gallbladder function regulation	CCKAR detection in rats; suitable for mechanistic studies related to the cholecystokinin receptor
EJ1515533	Mouse Cholecystokinin (CCK) ELISA Kit	BioReagent	Gallbladder function regulation	CCK detection in mouse models; suitable for studies of gallbladder contraction and bile discharge
EJ1515295	Pig Cholecystokinin (CCK) ELISA Kit	BioReagent	Gallbladder function regulation	CCK detection in porcine samples; suitable for studies of digestive regulation and gallbladder function
EJ1514639	Human Fatty Acid Binding Protein 1, Liver (FABP1) ELISA Kit	BioReagent	Hepatic lipid transport/auxiliary liver injury indicator	FABP1 detection in human samples; suitable for studies of hepatocellular fatty acid transport and liver injury
H1509865	Human L-FABP ELISA Kit	BioReagent	Hepatic lipid transport/auxiliary liver injury indicator	Detection of human liver-type fatty acid-binding protein; suitable for auxiliary evaluation of hepatic lipid metabolism and hepatocellular injury
M1510086	Mouse L-FABP ELISA Kit	BioReagent	Hepatic lipid transport/auxiliary liver injury indicator	Detection of mouse liver-type fatty acid-binding protein; suitable for mouse hepatic lipid metabolism and liver injury models
EJ1513082	Mouse Fatty Acid Binding Protein 1 (LFABP) ELISA Kit	BioReagent	Hepatic lipid transport/auxiliary liver injury indicator	LFABP detection in mice; suitable for studies of hepatic fatty acid transport and lipid metabolism
L777640	Hepatic Protein Isolation Kit	BioReagent, for protein analysis, for mammalian sample extraction	Liver tissue protein sample pretreatment	Liver tissue protein extraction; suitable for ELISA, protein analysis, and pretreatment for mechanistic indicator detection

Detection of hepatobiliary metabolism-related indicators should be combined according to the research objective. Cholestasis studies may prioritize TBA, TBIL, and DBIL; bilirubin metabolism studies may incorporate urinary bilirubin and urobilinogen; cholesterol homeostasis and gallstone studies should combine TC, FC, CE, and lipoprotein indicators. When mechanistic interpretation is required, regulatory factors such as CYP7A1, NPC1L1, LCAT, HL, FABP1/LFABP, and CCK can be further included.

For more related articles, please see below:

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