Effects of in utero and lactational exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on serum androgens and steroidogenic enzyme activities in the male rat reproductive tract

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) has been shown to impair reprodu ctive function of males in animal models, possibly due to a reduction in se rum androgen levels. Thus, TCDD may alter the testosterone biosynthetic pat hway in the testis or the conversion of testosterone to 5 alpha-dihydrotest osterone (DHT) in androgen target tissues. Pregnant Sprague Dawley rats wer e gavaged with TCDD (0, 0.2 or 1.0 mu g/kg) on day 15 of gestation only. TC DD caused a reduction in the body weight gain of the dams in both dose grou ps and a significant reduction in litter size in the higher dose group. Lit ters delivered normally and TCDD exposed male offspring grew at the same ra te as controls. Males were sacrificed at 15, 30, 45, 60, 90 and 120 d of ag e. Steroidogenic enzyme activities were determined in testicular microsomes and androgen target tissue nuclear fractions. Serum androgens were measure d by radioimmunoassay (RIA). At 30 d of age, rats exposed to 1.0 mu g/kg TC DD exhibited lower 17-hydroxylase activity (P < 0.05) and lower caput-corpu s epididymal weights (P < 0.05). At 45 d of age, the same treatment resulte d in testicular 3 beta-HSD, 17 beta-HSD and 5 alpha-reductase activities th at were significantly greater (P < 0.05) but, conversely, serum androgens w ere one quarter the values evident in controls (P < 0.05). At the other age s, no differences were observed in serum androgens and, with the exception of lower 17 beta-HSD activity at 90 d of age (P < 0.05), no other differenc es in testicular steroidogenic enzyme activities were found. Su-reductase a ctivities in the androgen target tissues were also unchanged. Histological examination of testes showed that the spermatogenic profile was identical t o controls at all ages. reserved.