The involvement of dopamine in the regulation of steroidogenesis in rat ovarian cells.

To investigate a role for dopamine (DA) in steroidogenesis in the rat ovary, ovarian cells of pregnant-mare-serum gonadotropin (PMSG)-treated rats were incubated with DA agonists, antagonists, adrenergic drugs and beta-blocker for 1 h. DA, norepinephrine (NE) and isoproterenol (Iso) increased the level of progesterone (P4) and cAMP in the conditioned medium. D1 agonists (SKF38393, SKF82526J, CY208-243) increased P4 secretion, while the D2 agonist, bromocriptine, showed no significant effect on P4 secretion. The effect of NE or Iso was inhibited by the beta-blocker propranolol (Pro), but was not suppressed by the D2 antagonist, domperidone. The effects of D1 agonists were suppressed by bulbocapnine (Bul), while neither Pro nor the D2 antagonist, domperidone, affected the levels of P4. The D1 receptor was demonstrated in the PMSG-treated rat ovary, and its Bmax was 1.33 fmol/mg tissue and the Kd was 0.357 nM. These results suggest that DA has a direct stimulatory effect on P4 secretion in PMSG-treated rat ovarian cells through they D1 receptor. The observed action may indicate a physiological role for DA in the regulation of ovarian functions in rats.