Di-n-Butyl Phthalate Disrupts the Expression of Genes Involved in Cell Cycle and Apoptotic Pathways in Mouse Ovarian Antral Follicles

Di-n-butyl phthalate (DBP) is present in many consumer products, such as infant, beauty, and medical products. Several studies have shown that DBP causes reproductive toxicity in rodents, but no studies have evaluated its effects on ovarian follicles. Therefore, we used a follicle culture system to evaluate the effects of DBP on antral follicle growth, cell cycle and apoptosis gene expression, cell cycle staging, atresia, and 17 beta-estradiol (E-2) production. Antral follicles were isolated from adult CD-1 mice and exposed to DBP at 1, 10, 100, and 1000 mu g/ml for 24 or 168 h. Follicles treated with vehicle or DBP at 1-100 mu g/ml grew over time, but DBP at 1000 mu g/ml significantly suppressed follicle growth. Regardless of effect on follicle growth, DBP-treated follicles had decreased mRNA for cyclins D2, E1, A2, and B1 and increased p21. Levels of the proapoptotic genes Bax, Bad, and Bok were not altered by DBP treatment, but DBP 1000 mu g/ml increased levels of Bid and decreased levels of the antiapoptotic gene Bcl2. DBP-treated follicles contained significantly more cells in G(1) phase, significantly less cells in S, and exhibited a trend for fewer cells in G(2). Although DBP did not affect E-2 production and atresia at 24 h, follicles treated with DBP had reduced levels of E-2 at 96 h and underwent atresia at 168 h. These data suggest that DBP targets antral follicles and alters the expression of cell cycle and apoptosis factors, causes cell cycle arrest, decreases E-2, and triggers atresia, depending on dose.