Effect of insulin-like growth factor-I on cholesterol side-chain cleavage cytochrome P450 messenger ribonucleic acid expression in ovarian theca-interstitial cells stimulated to differentiate in vitro.

Currently available evidence supports the hypothesis that insulin-like growth factor-I (IGF-I) may play a role in stimulating ovarian theca-interstitial cell (TIC) differentiation in preantral follicles. The purpose of the present studies was to examine the potential role of IGF-I in TIC differentiation by determining the effects of IGF-I on cholesterol side-chain cleavage cytochrome P450 (P450SCC) mRNA expression in TIC stimulated to differentiate in vitro. TIC were isolated from the ovaries of hypophysectomized immature rats by Percoll gradient centrifugation and cultured in the presence and absence of LH and IGF-I up to 6 days. At various times cytoplasmic RNA was extracted from the TIC and P450SCC mRNA was measured by specific assay using reverse transcription followed by the polymerase chain reaction. Increasing concentrations of LH (0-1 microgram/ml) stimulated a dose-related increase in P450SCC mRNA (ED50 = 36.2 +/- 5.5 ng/ml) which reached maximal levels at 100 ng/ml of LH. Addition of IGF-I (30 ng/ml) caused a small increase in P450SCC mRNA over TIC treated with LH alone but did not alter the ED50 for LH stimulation. IGF-I alone also stimulated an increase in P450SCC mRNA which reached approximately 3-fold over unstimulated levels at 100 ng/ml. In the presence of LH, IGF-I stimulated a dose-related increase in P450SCC mRNA (ED50 = 1.2 +/- 0.05 ng/ml). Time-course studies revealed that expression of P450SCC mRNA was greatest at 2 days in TIC treated with IGF-I alone, LH alone or LH plus IGF-I and then declined at 4 and 6 days.(ABSTRACT TRUNCATED AT 250 WORDS)