EFFECTS OF 6-HYDROXYDOPAMINE ON TESTOSTERONE PRODUCTION BY MOUSE LEYDIG-CELLS IN-VITRO

Increasing doses (15 to 1000 mu g/ml) of 6-hydroxydopamine (6-OHDA) st imulated, then suppressed testosterone production by mouse Leydig cell s incubated for 3 h in vitro. The stimulating doses ranged between 50 and 100 mu g/ml, with maximal effects occurring at 30 to 60 minutes af ter the start of the treatments. At doses of 500 mu g/ml, 6-OHDA exhib ited inhibitory effects. When added to Leydig cell incubations togethe r with stimulating doses of luteinising hormone (LH), 1-(3',4'-dihydro xyphenil)2-isopropylaminoethanol (L-isoproterenol) or 8-bromoadenosine 3':5'-cyclic monophosphate (8-Br-cAMP), 6-OHDA abolished the effects of the latter compounds. Prolactin and prostaglandin E(2) (PGE(2)) inh ibited the stimulating effects of 8-Br-cAMP but not LH. It is proposed that the actions of 8-OHDA affect intracellular sites yet to be ident ified, thereby inhibiting testosterone production by mouse Leydig cell s. Same of the actions of 6-OHDA seem to be medicated via beta-adrener gic receptors as the latter abolishes the stimulatory effects of L-iso proterenol, a potent beta-adrenergic agonist. However, the inability o f stimulatory doses of LH and 8-Br-cAMP to reverse the inhibitory effe cts of 6-OHDA point to the possibility that other actions of 6-OHDA ma y by relayed via a second messenger system separate from that involvin g cAMP.