Positive Control Study for the Intact Immature Swiss- Webster Mouse Uterotrophic Assay

摘要

Endocrine disruptors are chemicals in the environment that can disrupt the normal functions of hormones in the body. A majority of these endocrine disruptors are estrogenic. The most commonly used in vivo method to test the estrogenicity of substances is the uterotrophic assay. This assay has many procedural variations, but works on the principle of measuring increase of uterine weight (uterotrophic response) as a response to estrogenic chemicals in animals with low levels of endogenous estrogens. Positive control study should be performed before using this method for the first time. The Developmental Biology laboratory in ITB plans to test pollutants for estrogenicity, therefore this study is conducted. In this study, intact immature Swiss-Webster mice (Mus musculus L.) were used. Twenty four female mice were weaned at 21 days old and divided into four groups. Each group were given 0, 5, 50, or 500 μg/kg bw 17β-estradiol daily for three days. 17β-estradiol dissolved in 10% ethanol-corn oil were administered via subcutaneous injection to the dorsoscapular and lumbar region with an injection volume of 0,05 mL/10 g bw. Twenty four hours after the last injection, the mice were killed by cervical dislocation and then dissected. The uterus is removed and weighted to obtain the uterine wet weight and blotted weight, and then processed for histological observation. Uterine gland number were calculated form transverse sections of the uterus, luminal epithelium height and cell number were measured form longitudinal sections. Both wet and blotted uterine weights per body weight ratio increased in a dose dependent manner with significant differences to controls (p<0.05). Uterine gland number and luminal epithelium cell height also increase in a dose dependent manner with significant differences to controls (p<0.05). Cell number showed no significant difference to controls. The results are consistent with the hypothesis except for cell number which did not differ significantly from controls. Based on the results, the immature mouse uterotrophic assay can be used as a test for estrogenicity except for the cell number parameter.