Estradiol and luteinizing hormone regulation of insulin-like growth factor binding protein production by bovine granulosa and thecal cells

To determine the effects of estradiol and luteinizing hormone (LH) on insulin-like growth factor-binding protein (IGFBP) production by bovine granulosa and thecal cells, both cell types were collected and cultured in serum-free medium with various hormone treatments, arranged in three experiments. In thecal cells, insulin stimulated (p<0.05) production of IGFBP-2 and IGFBP-5, but had no effect (p>0.10) on IGFBP-3 and IGFBP-4 production; LH stimulated (p<0.05) production of IGFBP-2 and IGFBP-3 but had no effect (p>0.05) on IGFBP-4 and IGFBP-5. Estradiol had no effect (p>0.10) on IGFBP-2, IGFBP-3, IGFBP-4, and IGFBP-5 production by thecal cells. Production of IGFBP-2/-5 by granulosa cells from small follicles was inhibited (p<0.05) by insulin, but estradiol and LH did not influence (p>0.10) insulin’s inhibitory effect on basal IGFBP-2/-5 production. Insulin, LH, and estradiol each inhibited IGFBP-4 production by small-follicle granulosa cells, but their effects were not additive. IGFBP-3 was not produced by small-follicle granulosa cells. In large-follicle granulosa cells, insulin and LH inhibited (p<0.05) production of IGFBP-2/-5 and IGFBP-3, whereas estradiol had no effect. Insulin alone had no effect (p>0.10) on production of IGFBP-4, but estradiol and LH inhibited (p<0.05) production by large-follicle granulosa cells, and their effects were not additive. These results suggest that production of IGFBP-2, IGFBP-3, IGFBP-4, and IGFBP-5 by granulosa and thecal cells is differentially affected by hormonal stimuli.