Altered gene profiles in fetal rat testes after in utero exposure to di(n-butyl) phthalate

Di(n-butyl) phthalate (DBP) has antiandrogenic-like effects on the developi ng reproductive tract in the male rat and produces regions of interstitial cell hyperplasia and gonocyte degeneration in the developing fetal testes a t maternal doses of 100-500 mg/ kg/day. Neither DBP nor its primary metabol ites interact with the androgen receptor in vitro. The present study was pe rformed to examine gene expression in the fetal rat testes following in ute ro DBP exposure. Pregnant Sprague-Dawley rats received corn oil, DBP (500 m g/kg/day), or flutamide (reference antiandrogen, 50 mg/kg/day) by gavage da ily from gestation day (GD) 12 to 21. Dose levels were selected to maximize fetal response with minimal maternal toxicity. Testes were isolated on GD 16, 19, and 21. Global changes in gene expression were determined by microa rray analysis. Selected genes were further examined by quantitative RT-PCR. DBP, but not flutamide, reduced expression of the steroidogenic enzymes cy tochrome P450 side chain cleavage, cytochrome P450c17, and steroidogenic ac ute regulatory protein. Testicular testosterone and androstenedione were de creased on GD 19 and 21, while progesterone was increased on GD 19 in DBP-e xposed testes. Testosterone-repressed prostate message-2 (TRPM-2) was upreg ulated, while c-kit (stem cell factor receptor) mRNA was downregulated foll owing DBP exposure. TRPM-2 and bcl-2 protein staining was elevated in GD 21 DBP-exposed Leydig and Sertoli cells. Results of this study have led to th e identification of several possible mechanisms by which DBP can induce its antiandrogenic effects on the developing male reproductive tract without d irect interaction with the androgen receptor. Our results suggest that the antiandrogenic effects of DBP are due to decreased testosterone synthesis. In addition, enhanced expression of cell survival proteins such as TRPM-2 a nd bcl-2 may be involved in DBP-induced Leydig cell hyperplasia, whereas, d ownregulation of c-kit may play a role in gonocyte degeneration. Future stu dies will explore the link between these identified gene expression alterat ions and ultimate adverse responses.