Inhibition of basal and stimulated progesterone synthesis by dichlorodiphenyldichloroethylene and methoxychlor in a stable pig granulosa cell line

The effects of the insecticide dichlorodiphenyldichloroethylene (DDE) and m ethoxychlor in a stable pig granulosa cell line, JC-410, were investigated. The studies of DDE and methoxychlor were conducted in combination with stu dies of cholera toxin, the protein kinase A activator that stimulates cAMP and progesterone synthesis and gene expression of P450 cholesterol side cha in cleavage (P450scc), which converts cholesterol to pregnenolone. Administ ration of DDE at 3000 and 10 000 ng ml(-1) was found to decrease progestero ne synthesis 0.49- and 0.25-fold, respectively, and to block the stimulator y effect of 100 ng cholera toxin ml(-1), after 24h incubation. At 1-100 ng ml(-1), methoxychlor did not affect progesterone synthesis after 48h incuba tion. However, 1000ng methoxychlor ml(-1) decreased progesterone synthesis 0.32-fold, and both 100 and 1000 ng methoxychlor ml(-1) blocked the stimula tory effect of cholera toxin. At 3000 and 10 000 ng ml(-1), DDE decreased c AMP synthesis 0.66- and 0.36-fold, respectively. At 300, 3000 and 10 000 ng ml(-1), DDE also decreased cholera toxin-stimulated cAMP synthesis 0.84-, 0.68-, and 0.52-fold, respectively. Administration of 1-100 ng methoxychlor ml(-1) did not affect basal or cholera toxin-stimulated cAMP synthesis. Ch olera toxin increased P450scc mRNA 1.4-fold after 24 h incubation, while 30 00 and 10 000 ng DDE ml(-1) led to 0.39- and 0.18-fold reductions, respecti vely. The stimulatory effect of cholera toxin on P450scc mRNA was blocked b y 3000 and 10 000 ng DDE ml(-1). Cholera toxin increased P450scc mRNA 3.48- fold after 48 h incubation, while 100 and 1000 ng methoxychlor ml(-1) incre ased P450scc mRNA 1.79- and 3.0-fold, respectively, and further increased t he stimulatory effect of cholera toxin 6.47- and 5.44-fold, respectively. T he results of the present study indicate that DDE inhibits granulosa cell s teroidogenesis by affecting cAMP production and P450scc gene expression. Ho wever, methoxychlor appears to inhibit steroidogenesis by a mechanism occur ring before the conversion of cholesterol into pregnenolone.