RAT SERTOLI-CELL FACTOR AND LEYDIG-CELL TESTOSTERONE SYNTHESIS - MECHANISM OF ACTION

In Percoll purified Leydig cells fi om mature rat incubated in Ham F12/DME medium, we have demonstrated that the testosterone production (I ng/10(6) Leydig cells/3 h) is increased 9 fold in presence of a saturating amount of oLH but diminished when larger doses of gonadatropin are used However, if SCM or STM is added together with oLH to the Leydig cell incubation medium, a further increase (69 %) of testosterone output is noticed. Obviously, when the testosterone production is low consecutive to a desensitizating dose of oLH the STM or SCM improves at least 2 fold the steroid synthesis. Therefore, the paracrine factor (or factors) presents in SCM (or STM) which is testis specific and acts in synergy with dbcAMP and 22R-hydroxycholesterol, uses an alternative pathway to improve rat Leydig cell testosterone production since its biological effect is highly potent in absence and in presence of oLH Therefore, these data bring new insights in the regulation of rat Leydig cell steroidogenesis through cAMP-independent channel suggesting either an increase of the cholesterol side chain cleavage activity and/or availability of the cholesterol to mitochondria.