Effects of testicular macrophage-conditioned medium on Leydig cells in culture.

Conditioned medium from cultures of testicular macrophages was capable of stimulating testosterone production in a dose-dependent manner when added to Leydig cells in vitro. Significant stimulation of testosterone production by Leydig cells was observed after 4 h of exposure to testicular macrophage-conditioned medium (TMCM) and thereafter increased progressively for up to 24 h. Treatment of Leydig cells with TMCM together with a maximal dose of LH resulted in greater production of testosterone by Leydig cells than with either agent when used separately. Conditioned medium from macrophages treated with FSH was twice as potent as TMCM from untreated cells. This dose of FSH had no direct effect on Leydig cells. Conditioned medium from cultures of peritoneal macrophages had less effect on testosterone production by Leydig cells than testicular macrophage-conditioned medium. It is proposed that secretory products from testicular macrophages play an important role in testicular function.