Functional dopamine-1 receptors and DARPP-32 are expressed in human ovary and granulosa luteal cells in vitro

The catecholamines norepinephrine and dopamine (DA) are present in the huma n ovary; in particular, in follicular fluid. Norepinephrine activates ovari an alpha- and beta-adrenergic receptors and modulates ovarian steroidogenes is, but the significance of ovarian DA is unclear. We examined whether a DA , receptor of the D1-subtype (D1-R) is present in human ovary and in cultur ed human granulosa luteal cells (GC). Using RT-PCR, we cloned complementary DNAs from adult human ovarian and GC messenger RNAs, which are identical t o the human D1-R sequence. In ovarian sections, D1-R protein was identified (by immunohistochemistry) in granulosa cells of large antral follicles, ce lls of the corpus luteum, as well as in cultured GC. An immunoreactive band of approximately Mr 50,000 was found in cultured luteinized GC using the s ame antiserum in Western blots. The D1-R in these cells was functional, bec ause DA, alone or in the presence of the beta-receptor antagonist propranol ol, caused cellular contraction. The selective D1-R agonist SKF-38393 induc ed a similar change in cytomorphology and increased the levels of media cAM P. SKF-38393 failed, however, to significantly affect basal and hCG-stimula ted progesterone release in vitro, indicating that the activation of the D1 -R was not directly linked to synthesis of progesterone, the major steroid of human GC. Estradiol synthesis likewise was not affected. Using RT-PCR an d immunohistochemistry, we found that GC express DA- and cAMP-regulated pho sphoprotein of Mr 32,000 (DARPP-32), a protein typically associated with ne urons bearing the D1-R. In cultured GC, DA and SKF-38393 induced increased threonine-phosphorylation of DARPP-32, even in the presence of propranolol but not in the presence of D1-R antagonist SCH-23390. Taken together, the p resence of DA and a functional DA receptor and DARPP-32 indicate that a nov el, physiological regulatory pathway involving DA. exists in the human ovar y.