Improvement of the Koch method of acute toxicity testing
Improvement of the Koch method of acute toxicity testing
1, study the design of acute toxicity test of chemicals, master the determination of LD50.
2. Observe the toxic reaction of phoxim.
Operation method
Improvement of the Koch method of acute toxicity testing
Principle
Acute toxicity test refers to the toxic reaction and death of the test animals after a large dose of drug administration. The size of the toxicity of the drug is commonly used to express the lethal dose of the animal, because the physiological indicators of animal life and death are more obvious, objective and easy to grasp than other indicators. The determination of lethal dose is also more accurate. In the determination of lethal dose at the same time, should also carefully observe whether the animal shrugged hair, tired lying, pale or congested ear shells, protruding eyes, staggering, muscle paralysis, respiratory difficulties, coma, convulsions, urinary and fecal incontinence and other adverse reactions. The lethal dose is often determined by the LD50. LD50 is the dose that can cause half of the death of the test animals, the logarithm of the lethal dose of the drug, expressed by the symbol LD50. Because the determination of LD50 is simple, reliable and stable, it has become an important constant to mark the degree of acute poisoning of animals.There are various methods for the determination of LD50, such as Bliss method, improved Kou's method, simplified chance unit method, cumulative interpolation method, chance unit-weighted linear imputation method, etc. Although the above methods have their own characteristics, they are not the same as the other methods. Although each of the above methods has its own characteristics, they all have common requirements: (1) Animals: Healthy mice weighing 17-22 grams (the weight difference in the same test shall not exceed 4 grams) or healthy rats weighing 120-150 grams (the weight difference in the same test shall not exceed 10 grams) are used as experimental animals. The animals should be of the same sex or half male and half female. (2) Route of administration: Try to make the actual route of exposure of the test animal and human to the test substance consistent. Food toxicology generally choose the oral route. Gavage is mainly used. (3) Test period and observation index: Observe at least 7 days after administration. During the observation period, the toxic reactions of animals and the distribution of dead animals should be recorded day by day. (4) Before the formal test, a small number of animals should be used for the pre-test, and the lethal dose range of 0% and 100% mortality caused by the test drug should be roughly measured, and then the formal test should be arranged. The number of formal test groups shall not be less than three dose groups, generally 4-5 dose groups are used, and the number of animals in each group is 10-20. (5) When reporting the LD50, it is necessary to indicate the species and strain of the experimental animals, gender, weight range, route of administration and the number of animals in each dose group, etc. It is also necessary to indicate the preparation method of the test drug, the dose of the drug, the ratio between the doses of each group (generally 0.65-0.85 is preferred), the volume of the drug, the time of observation, and the method of calculation. The 95% confidence limit of the LD50 should also be indicated.
Materials and Instruments
mouse Move 1、Pre-test experiment: The purpose of pre-test experiment is to find out the dose that causes 0% (Dn) and 100% (Dm) of the animals to die, so as to arrange the formal experiment. Pre-test experiments are generally conducted with a small number of animals (6-9 mice), the animals are randomly divided into 3 groups, and the dose ratio between groups is generally 1:0.5 or 1:0.7. The dosage ratio between groups is usually 1:0.5 or 1:0.7. The dosage of the drug by gavage or intraperitoneal injection should be 0.2 ml/10 g body weight. Effect of phoxim on the mortality of mice For more product details, please visit Aladdin Scientific website.
Phoxim
Syringes Gavage needles Mouse cages
Pre-test experiments should be conducted until Dn and Dm are identified before formal experiments are scheduled.
2. Formal experiment: Set up 4-6 dose groups, up to 10 groups, within the dose range of Dn and Dm measured in the pre-test experiment. The ideal result is to have 2 to 3 groups above and below the LD50. The smaller the number of groups, the less accurate the results. The number of animals in each dose group should be equal, at least 10 animals (the principle of stratified randomization should be noted when grouping). The maximum response rate should be 100%, the minimum response rate should be 0%, or at least the response rate should be close to 100% or 0%. The dose ratio between groups (1:K), commonly used 1:0.8 or 1:0.75. If there are duplicate 100% and 0% response rates for adjacent doses in the experiment, the adjacent group should be discarded, so that there is only one 100% response rate for the large dose group and only one 0% response rate for the small dose group.
After the grouping was completed and the doses of each group were calculated, the groups were instilled or injected with different doses of the test drug. In order to get the desired results, it is better to start the experiment from the middle dose, so that the response of the animals in the first few dose groups after receiving the drug can be used to judge the appropriateness of the dose at both ends, and to facilitate the adjustment of the dose and the number of groups. In order to improve the accuracy of the experiment and save the drug, the test drug can be configured according to the "low ratio dilution method". Even if the volume of the drug for each animal is equal (0.2ml/10g), the solutes are not equal. Poisoning reactions, mortality and deaths were observed and recorded on a daily basis after administration of the drug.
V. Recording and calculation of experimental results on the effect of phoxim on the mortality of mice
