EFFECTS OF INSULIN-LIKE GROWTH FACTOR I (IGF-I) ON STEROID PRODUCTION BY ISOLATED OVARIAN THECA AND GRANULOSA LAYERS OF PREOVULATORY COHO SALMON

摘要

The effects of recombinant human and salmon insulin-like growth factor-I (IGF-I) on in vitro steroid production by isolated theca and granulosa cell-layers of the preovulatory coho salmon ovary were examined. Prior to germinal vesicle breakdown (GVBD), IGF-I decreased basal theca cell-layer production of testosterone (T) and 17 alpha-hydroxy-progesterone (17OH-P) and also inhibited the stimulatory effects of gonadotropin II (GTH II) on T production. After GVBD, IGF-I lowered the GTH II-induced production of both steroids by theca cells. In contrast, IGF-I enhanced the stimulatory effects of GTH II on conversion of 17OH-P ro 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (17,20 beta-P) by granulosa cells during final oocyte maturation.