High, not low-dose of stanozolol (Anabolic - androgenic steroid) impedes embryo implantation by attenuating endometrial receptivity in the mouse, Mus musculus

The present investigation is aimed at evaluating the efficacy of one of the anabolic -androgenic steroids, stanozolol (ST), on establishment and maintenance of pregnancy in mice. A total of 40 female mice were assigned to three experimental groups. Stanozolol was dosed subcutaneously (low-dose, 0.5 mg/kg bwt; high-dose, 5.0 mg/kg bwt or 1% alcohol-baseline control) for 30 consecutive days. On the 31st day, treatment was withdrawn. The estrous cycle was disrupted in both treatment groups and its resumption was dose dependent. Following estrous resumption, mice were allowed to mate. Results reveal that the low-dose ST-treated mice maintained gestation until term with reduced litter size, while high-dose-treated mice divulged vaginal plug at frequent intervals, indicating conception failure. Because pregnancy failure was noticed in high-dose-treated mice, they were autopsied on GD1.5 and 4.5. Interestingly, neither dose of stanozolol affected early embryonic development or blastocyst hatching. A decrease in the number of corpora lutea in both treated groups suggests it affects either ovulation or recruitment of follicles that occurs in each cycle for maturation. In high-dose-treated mice, decreased serum levels of estradiol, progesterone and increased testosterone along with downregulated endometrial expression of ERα and PR suggest the deficiency of steroid hormones and their respective receptors. Decreased ovarian expression of ERα, hyperexpression of PRLR, AR and abated progesterone secretion led to luteal dysfunction, consequently attenuating endometrial receptivity. Therefore, in high-dose-treated mice, decreased maternal estradiol and progesterone levels and their receptors during implantation hindered signaling to LIF and Hoxa-10, resulting in pragmatic implantation failure.