Growth hormone amplifies insulin-like growth factor I induced progesterone accumulation and P450scc mRNA expression

The interaction of growth hormone (GH) and insulin-like growth factor I (IGF-I) in the acquisition of progesterone biosynthetic capacity were examined in cultured porcine granulosa cells. Basal progesterone production was not affected (P > 0.05) by GH treatment. However, concurrent treatment with GH produced a 4.1-fold increase (539 versus 2214 ng/culture) in the IGF-I-stimulated accumulation of progesterone. GH potentiated IGF-I induced progesterone production in a dose and time dependent manner, with a time requirement of 48 h or less. The amplified effect of GH was not attributable to changes in cellular protein, DNA content, cell number, plating efficiency or cell viability. Moreover, Northern blot analyses revealed that GH enhanced IGF-I induced expression of the gene encoding cytochrome P450 side chain cleavage. These observations provide further evidence to support the role of GH in the regulation of ovarian steroidogenesis.