In vitro stimulation of steroidogenesis in rat testis by cholera enterotoxin

Inhibition of hormone-induced cyclic AMP production and steroidogenesis in interstitial cells by deglycosylated lutropin

We have investigated the ability of chemically deglycosylated ovine pituitary lutropin (DGLH) to stimulate cyclic AMP accumulation in rat interstitial cells in vitro. In sharp contrast to the native hormone which brought about a large increase in cyclic AMP levels, no significant response was indiced by DGLH even in the presence of the phosphodiesterase inhibitor, isobutyl methylxanthine. On the contrary, all preparations of DGLH tested were potent inhibitors of the action of the native hormone. The concentration of DGLH for inhibition of LH-induced cyclic AMP response was significantly lower than that required for inhibition of steroidogenesis. While inhibition of hormone-induced cyclic AMP response was complete, the inhibition of steroidogenesis in testicular cells by DGLH approached about 70-80%. Accumulation of cycli AMP induced by hCG was also effectively inhibited by DGLH suggesting that its inhibitory action is mediated via its binding to lutropin receptor(s) on interstitial cells. A recombinant of deglycosylated subunits, DG alpha + DG beta, had properties identical to that of DGLH.

Effects of prostaglandins on the action of luteinizing hormone in dispersed rat intestitial cells

Prostaglandins E1, E2, A1 and A2 at 10(-5) and 10(-4)M stimulated basal testosterone production in dispersed rat interstitial cells in vitro. They effectively inhibited steroidogenesis induced by ovine pituitary luteinizing hormone (LH) (0.2 nM), dibutyryl cyclic AMP-(DBC 0-5 mM), and cholera toxin (100 ng). PGF2 alpha (10(-3) to 10(-12)M) had no effect on either basal or hormonal or non-hormonal stimulated steroidogenesis in the cells. PGA1 and PGA2 were more effective inhibitors than PGE1 and E2. None of the PG's had any influence on 125I LH-receptor interaction. In view of this and the inhibition of DBC stimulated testosterone production, it may be suggested that the PG inhibition lies beyond the receptor-cyclic AMP formation step.