PRESENCE IN MOUSE SERTOLI CELL-CONDITIONED MEDIUM OF A FACTOR THAT EXPRESSES AVP-LIKE INHIBITION OF STEROIDOGENESIS BY MOUSE LEYDIG-CELLS IN LONG-TERM CULTURE

The influence of spent medium from immature mouse Sertoli cells (SCM) on testosterone production by purified Leydig cells was investigated a nd compared to that of AVP, a potent local modulator of Leydig cell st eroidogenesis. SCM inhibited in a dose-dependent manner the hCG-stimul ated testosterone production, but was ineffective in basal conditions. As is known for AVP, (i) a lag period of 72 h was prerequisite for SC M to inhibit Leydig cell function; (ii) the main effect of SCM was loc ated at a step beyond the receptor-adenylate cyclase system, since the hCG- and 8-bromo-cAMP-stimulated testosterone productions were simila rly affected. The possibility that the effect of SCM may be related to AVP-like molecule(s) is also supported by the observations that at ma ximal concentrations the inhibitory effects of AVP and SCM were not ad ditive and that the inhibition of testosterone production was largely (65%) reversed by the presence of [(beta-mercapto-beta, beta-cyclopent amethylenepropionyl(1), O-Me-Tyr(2),Arg(8))-vasopressin], a selective vasopressor antagonist. These data indicate that Sertoli cells produce in vitro potent inhibitory factors of Leydig cell steroidogenesis. Th ey provide additional evidence that one of these bioactive factors has an effect on Leydig cell function similar to that of AVP.