Alfa 1 adrenergic potentiation of progesterone accumulation stimulated by vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) in cultured rat granulosa cells.

OBJECTIVE: VIP and PACAP, two structurally related peptides, stimulate c AMP, steroidogenesis and progesterone (PROG) release from cultured rat granulosa cells. VIP and PACAP(38) are known to mimic the effects of beta-adrenergic receptor stimulation in the rat pinealocytes causing an increased melatonin synthesis. These effects were markedly potentiated by alpha(1) adrenergic receptor stimulation.

METHODS: We examined the influence of phenylonephrine (PHEN) (10(-4) M and 10(-5) M)-alpha(1) adrenergic receptor agonist and fenoterol (FEN) (10(-5) M)-beta(2) adrenergic receptor agonist on PROG accumulation stimulated by VIP (10(-6) M) and PACAP (10(-7) M) in cultured ovarian granulosa cells of cyclic rats (diestrus) after 2 h and 24 h incubation. The PROG concentrations in supernatants were measured with RIA tests.

RESULTS: VIP, PACAP(38), PHEN and FEN stimulated PROG accumulation after 2 h incubation. The PROG accumulation stimulated both by FEN and VIP, and by FEN and PACAP(38) was not additive. PROG accumulation stimulated by VIP and PACAP(38) was strongly potentiated by PHEN-alpha(1) adrenergic agonist.

CONCLUSION: The alpha(1) adrenergic potentiation of VIP and PACAP(38) stimulatory effects on PROG release from granulosa cells culture was found. VIP, PACAP(38) and beta(2) adrenergic receptors activation may share the same postreceptor mechanism. There exists simultaneous activation of different receptors -- peptidergic and adrenergic ones in cultured granulosa cells of adult cyclic rat.