Effects of Benzo(a)pyrene on the endometrial receptivity and embryo implantation in mice: An experimental study

Background: Benzo(a)pyrene (BaP) as an environmental pollutant is ubiquitous in theenvironment and it has destructive effects on human health. So far, various studies havedemonstrated that BaP can cause adverse effects on the female reproductive system,but the existing information is limited about the effects of BaP on the endometrialreceptivity and embryo implantation.Objective: The aim of this study was to investigate the effects of BaP on theendometrial receptivity and implantation in mice.Materials and Methods: In this experimental study, 40 pregnant BALB/c mice weredivided into 5 groups (n = 8/each) as follows: experimental groups received the dosesof 100 μg/kg, 200 μg/kg, and 500 μg/kg BaP dissolved in corn oil, the control groupreceived normal saline and sham group received corn oil. Pregnant mice administeredthese solutions from Day 1 to Day 5 of gestation by gavage. On Day 6, the mice weresacrificed. Then their embryos were counted and the hormonal, morphological andmolecular analyses were performed on the endometrial tissue.Results: The data revealed that BaP reduces estrogen and progesterone levels,decreases the number of implantation site, endometrium thickness, uterine lumendiameter, stromal cells and endometrial glands, and blood vessels in the endometrium.However, the expression of Activin receptor-like kinase 5 and E cadherin genes was notchanged by BaP with different doses.Conclusion: The finding of this study showed that BaP can change estrogen andprogesterone levels, and endometrial morphology leads to impairing the endometrialreceptivity and decreasing the number of implantation site.

Keywords:

Benzo(a)pyrene , Embryo implantation , Estrogen , Progesterone , ALK5 , E-cadherin