title: 25-Hydroxycholesterol-supported and 8-bromo-adenosine 3',5'-monophosphate-stimulated testosterone production by primary cultures of two populations of rat Leydig cells.
abstract: Previous studies from this laboratory have demonstrated the presence of two populations of rat Leydig cells (I and II), which differ in their capacity for hCG- or cAMP-stimulated testosterone production. In the present study, we examined the metabolism of 25-hydroxycholesterol in primary cultures of both populations of Leydig cells. 25-Hydroxycholesterol bypasses the cAMP-dependent transport mechanism to the mitochondrial cytochrome P-450 side-chain cleavage enzyme (P-450scc) required by cholesterol and thus provides an index of the relative activity of P-450scc. Incubation of Leydig cells with increasing concentrations of 25-hydroxycholesterol resulted in a concentration-dependent increase in the amount of testosterone produced, with maximal amounts in both populations being reached at 25-hydroxycholesterol concentrations of 5 microM or greater. Population II produced more than twice as much testosterone as population I Leydig cells, whether incubated with 25-hydroxycholesterol or with 8-bromo-cAMP. Each population of Leydig cells produced 2.5-fold greater amounts of testosterone when incubated with 25-hydroxycholesterol than when incubated with 8-bromo-cAMP. In both populations of Leydig cells, cAMP-stimulated testosterone production was not different in cells cultured for 24 h from that in freshly isolated Leydig cells. These data suggest that cholesterol transport to P-450scc limits maximal testosterone production, and that the difference in hCG- or cAMP-stimulated testosterone production between the two populations of Leydig cells is primarily due to differences in P-450scc activity between the two populations and is not a result of population I consisting mostly of damaged Leydig cells.
mesh_terms: D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology*; D000818:Animals; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D006888:Hydroxycholesterols / Q000494:pharmacology*; D007985:Leydig Cells / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D011284:Pregnenolone / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013739:Testosterone / Q000096:biosynthesis*
chemical_list: D006888:Hydroxycholesterols; D015124:8-Bromo Cyclic Adenosine Monophosphate; D013739:Testosterone; D011284:Pregnenolone; C007997:25-hydroxycholesterol