GROWTH-HORMONE AMPLIFIES INSULIN-LIKE GROWTH-FACTOR-I INDUCED PROGESTERONE ACCUMULATION AND P450SCC MESSENGER-RNA EXPRESSION

The interaction of growth hormone (GH) and insulin-like growth factor I (IGF-I) in the acquisition of progesterone biosynthetic capacity wer e examined in cultured porcine granulosa cells. Basal progesterone pro duction was not affected (P > 0.05) by GH treatment. However, concurre nt treatment with GH produced a 4.1-fold increase (539 versus 2214 ng/ culture) in the IGF-I-stimulated accumulation of progesterone. GH pote ntiated IGF-I induced progesterone production in a dose and time depen dent manner, with a time requirement of 48 h or less. The amplified ef fect of GH was not attributable to changes in cellular protein, DNA co ntent, cell number, plating efficiency or cell viability. Moreover, No rthern blot analyses revealed that GH enhanced IGF-I induced expressio n of the gene encoding cytochrome P450 side chain cleavage. These obse rvations provide further evidence to support the role of GH in the reg ulation of ovarian steroidogenesis.