Expression of cytochrome P450 17alpha-hydroxylase/C17-20 lyase in the fetal rat testis is reduced by maternal exposure to exogenous estrogens.
Testosterone is required for normal development of the male reproductive tract. Synthesis of testosterone occurs in the Leydig cells and is dependent upon the expression of several enzymes, including cytochrome P450 17alpha-hydroxylase/C17-20-lyase (P450c17), which is highly regulated within the testis. The aim of the present study was to investigate whether maternal exposure to estrogenic chemicals was able to affect Leydig cell function in the developing male fetus at the time of masculinization. Pregnant rats were injected sc with diethylstilbestrol (DES; 100 or 500 micrograms/kg), 4-octylphenol (OP; 100 or 600 mg/kg), or vehicle (oil, control) on days 11.5 and 15.5 postcoitum. Doses were chosen to reflect the reported estrogenic potency of the chemicals in vitro. On day 17.5, fetal testes were fixed before performing in situ hybridization and immunocytochemistry, used for extraction of RNA, or homogenized in phosphate buffer for determination of 17alpha-hydroxylase enzyme activity. There was no difference between fetuses from control and treated mothers in either the overall histology of the testes or the apparent number of Leydig cells, as determined by immunocytochemistry with an antibody directed against 3beta-hydroxysteroid dehydrogenase. However, there was a consistent and striking reduction in the amount of P450c17 detected by immunocytochemistry in testes from the groups given the higher dose of DES or OP. These observations were supported by measurement of 17alpha-hydroxylase activity, which was significantly reduced compared with that in controls (6.25 +/- 0.65 pmol/testis x min) in fetuses from animals treated with 100 micrograms/kg DES (4.27 +/- 0.39; P < 0.05), 500 micrograms/kg DES (1.4 +/- 0.47; P < 0.001), or 600 micrograms/kg OP (4.25 +/- 0.33; P < 0.05). RT-PCR and in situ hybridization revealed that these changes were mirrored by reductions in P450c17 messenger RNA in testes from fetuses from treated mothers compared with control levels. In conclusion, maternal treatment with either a potent sythetic estrogen (DES) or a putative environmental estrogen (OP) results in reduced expression of the messenger RNA and protein for P450c17 in fetal Leydig cells. These results, therefore, provide a mechanism by which inappropriate exposure of the fetus to estrogenic chemicals might have an adverse effect on fetal steroid synthesis and masculinization.
Majdic
G
G
Medical Research Council Reproductive Biology Unit, Edinburgh, UK.
Sharpe
R M
RM
O'Shaughnessy
P J
PJ
Saunders
P T
PT
D000446:Aldehyde-Lyases / Q000096:biosynthesis*; D000818:Animals; D001483:Base Sequence; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis*; D004054:Diethylstilbestrol / Q000008:administration & dosage*; D004968:Estrogens, Non-Steroidal / Q000008:administration & dosage*; D005260:Female; D007985:Leydig Cells / Q000378:metabolism; D008297:Male; D008431:Maternal-Fetal Exchange; D008969:Molecular Sequence Data; D010636:Phenols / Q000008:administration & dosage*; D011247:Pregnancy; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D013254:Steroid 17-alpha-Hydroxylase; D013737:Testis / Q000196:embryology / Q000201:enzymology*
D004968:Estrogens, Non-Steroidal; D010636:Phenols; D012333:RNA, Messenger; D004054:Diethylstilbestrol; C080417:4-octylphenol; D003577:Cytochrome P-450 Enzyme System; D013254:Steroid 17-alpha-Hydroxylase; D000446:Aldehyde-Lyases