Effect of growth hormone releasing hormone on luteinizing hormone stimulated progestin biosynthesis in cultured rat ovarian granulosa cells

Abstract

In the present study, we examined the effects of growth hormone releasing hormone (GHRH) on luteinizing hormone (LH)-stimulated progestin biosynthesis. Granulosa cells from pregnant mare serum gonadotropin (PMSG)-treated immature rats were cultured in vitro in the absence or presence of ovine National Institute of Health LH (100 ng/ml) with various doses of GHRH (10-9, 10-8 and 10-7 mol/l)for 24 h. At the end of the incubation period, the incubation media were collected and levels of progesterone, 20a-hydroxypregn-4-en-3-one and cyclic adenosine 3’, 5‘-monophosphate (cAMP) were measured. GHRH significantly stimulated progesterone production and cAMP accumulation in media in a dose-dependent manner in the basal state (p < 0.01 and p < 0.001, respectively). In the presence of LH, GHRH significantly inhibited LH-stimulatedprogesterone production in a dose-dependent manner (p < 0.01), whereas increasing concentrations of GHRH produced progressive increases in cAMP accumulation (p < 0.05). Since increasing concentrations of GHRH produced progressive decreases in the ratio of progesterone to 20a-hydroxypregn-4-en-3-one production in the LH-stimulated state (p < 0.01), GHRH may be involved in modulation of key steroidogenic steps concerned with progesterone degradation rather than formation in LH-stimulated rat granulosa cells. These results suggest that GHRH may regulate the effects ofLH in granulosa cells and play an important role in the reproductive process.