Effect of recombinant insulin like growth factor-1 on caprine granulosa cell steroidogenesis, in vitro

Besides gonadotropins various other peptide factors have been implicated in the ovarian follicular growth and steroidogenesis. In this study, the effect of insulin like growth factor-1 on caprine granulosa cell steroidogenesis was investigated in vitro using serum free culture medium. Caprine granulosa cells were obtained from antral follicles classified into three classes: small, <3 mm; medium, 3-6 mm and large, >6 mm in diameter. IGF-1 (10-500 ng/ml) stimulated the secretion of estradiol and progesterone by granulosa cells from all three categories of follicles. However, the effect was more profound on cells from large follicles. IGF-1 (10-500 ng/ml) acted in synergy with FSH (100 ng/ml) to stimulate steroidogenesis by granulosa cells from all three categories of follicles, again the effect was more pronounced in cells from larger follicles. In summary, IGF-1 at physiological concentrations significantly influenced the steroidogenic activity of caprine granulosa cells cultured under serum free conditions. The results also suggest that estrogen and progesterone biosynthesis is differentially regulated by IGF-1 depending upon the size of the follicles from which the cells were obtained. (C) 1999 Elsevier Science B.V. All rights reserved.