Direct regulating effects of transforming growth factor beta on the Leydig cell steroidogenesis in primary culture.

ABSTRACT

The effect of transforming growth factor beta on testicular steroidogenesis was studied by using a model of immature porcine Leydig cells cultured in a chemically defined medium. Leydig cells were cultured in the presence of human or porcine purified TGF beta and the following parameters were measured cell proliferation, LH/hCG binding, and hCG-stimulated steroid hormone productions (DHEA, DHEAS and testosterone). Whereas TGF beta from the two sources had no effect on Leydig cell multiplication, it markedly inhibited LH/hCG-stimulated DHEA and DHEAS in a time- and dose-dependent manner. The maximal inhibitory effect of this peptide on LH/hCG binding (65% decrease), hCG-stimulated DHEA (77% decrease) and DHEAS (92% decrease) productions was observed with 2 ng/ml for 48 h of treatment. In contrast, TGF beta exerted a biphasic effect on hCG-stimulated testosterone production stimulating (110% increase) until 2 ng/ml and inhibiting (35% decrease) for higher concentrations. [125I]TGF beta was cross-linked to Leydig cells using disuccinimidyl suberate; cells affinity labelled with [125I]TGF beta exhibit a major labelled band of approx 280 kDa, which has the properties expected from a TGF beta receptor. These data demonstrate that TGF beta is a direct potent regulator of Leydig cell steroidogenic function and its effects are probably mediated via a specific receptor.