ABSTRACT
<p><b>OBJECTIVE</b>To investigate the effects of phytoestrogens (daidzein and genistein) on the testosterone production of rat Leydig cells and the possible mechanisms.</p><p><b>METHODS</b>Primary Leydig cells were obtained from 3-month old male SD rats using discontinuous Percoll density gradient centrifugation. The effects of phytoestrogens at various concentrations were evaluated by ELISA, with hCG as the positive control. The mRNA expression of P450 side-chain cleavage enzyme (P450scc) was analyzed by semi-quantitative RT-PCR.</p><p><b>RESULTS</b>Genistein at 0.1 micromol/L obviously promoted the secretion of testosterone and upregulated the mRNA level of P450scc. At a higher concentration of 5 micromol/L, however, both daidzein and genistein significantly inhibited the testosterone production of Leydig cells (P > 0.05).</p><p><b>CONCLUSION</b>Genistein can promote the testosterone production of Leydig cells at a low concentration (0.1 micromol/L), but both daidzein and genistein can inhibit it at a higher concentration ( >5 micromol/L).</p>