Differential effects of insulin-like growth factor-I and gonadotropins on the proliferative activity of two subgroups of granulosa cells: cumulus oophorus and mural granulosa cells

Abstract

Objective: To evaluate the physiological role of insulin-like growth factor-I (IGFI) and its interaction with gonadotropins in cell replication of two types of granulosa cells (cumulus oophorus, CC) and mural granulosa cells (MGC). Design: Controlled randomized study of the action and interaction of gonadotropins and IGFI on granulosa cell replication in the rat. Setting: A university reproductive biology laboratory. Intervention(s): The study examined the in vivo treatment with gonadotropins or an analogue of IGFI, long Arg 3-insulin-like growth factor (LR 3-IGFI), which does not bind to IGFI-binding proteins. Main Outcome Measure(s): Granulosa cell replication was evaluated by the use of 3H-thymidine incorporation. Result(s): It was noted that the CC replicate much faster than the MGC. These two types of granulosa cells have very different dose response curves to IGFI. Differential responses were seen in animal cells exposed to long Arg 3-insulin-like growth factor in vivo and then exposed to FSH and LH in vitro. Conclusion(s): Although murine granulosa cells show proliferative activity when they are exposed to IGFI, the two types, CC and MGC, respond differently. IGFI is not the sole mediator of the action of FSH, and these two chemicals may act independently or in concert.