Effects of estrogenic compounds on neonatal oocyte development

Abstract

In the mouse, oocytes develop in germline cysts that undergo breakdown resulting in primordial follicles, consisting of a single oocyte surrounded by granulosa cells. During this process, approximately two-thirds of the oocytes die. Exposure of female mice to environmental estrogens can alter oocyte development, limiting the number of primordial follicles that can be used for reproduction. Here we asked whether exposure to synthetic estrogens, diethylstilbestrol, ethinyl estradiol and bisphenol A affected perinatal oocyte development. Neonatal mice were injected with a low or high dose of each compound on postnatal days (PND) 1-4 and ovaries analyzed on PND5. Cyst breakdown, oocyte survival and follicle development were altered. The percentage of single oocyte was reduced from 84% in controls to 50-75%. The oocyte number per section was increased from 8 to 12-16. Follicle activation was reduced with 62% primordial follicles in controls to over 80% in most cases.