Production of insulin-like growth factor-I by granulosa cells but not thecal cells is hormonally responsive in cattle

To determine whether the hormonal regulation of IGF-I production differs be tween granulosa and thecal cells in cattle, granulosa and thecal cells from bovine follicles were collected, cultured for 2 d in medium containing 10% fetal calf serum, washed, and then treated for an additional 24 h in serum -free medium with various hormones. In Exp. 1, granulosa cells were treated with 0 or 100 ng/mL of insulin and(or) 50 ng/mL of follicle-stimulating ho rmone (FSH), insulin plus 10 ng/mL of epidermal growth factor, or insulin p lus 10 ng/mL of basic fibroblast growth factor. In Exp. 2, thecal cells wer e treated as described in Exp. 1 except that 100 ng/mL of luteinizing hormo ne (LH) was used instead of 50 ng/mL of FSH. In Exp. 3, granulosa and theca l cells were treated with 0 or 30 ng/mL of cortisol with or without 100 ng/ mL of insulin, 300 pg/mL of glucagon, or glucagon plus insulin. In Exp. 4, granulosa and thecal cells were treated with 0 or 300 ng/mL of estradiol wi th or without 100 ng/mL of insulin and(or) 100 ng/mL of LH. At the end of t reatment, medium was collected, concentrated with Centricon-3 concentrators , and assayed for IGF-I by radioimmunoassay. Cell numbers were determined b y Coulter counting at the end of culture. Thecal cells produced low amounts of IGF-I (0.48 +/- 0.04, 0.63 +/- 0.03, and 0.82 +/- 0.03 ng per 100,000 c ells per 24 h in Exp. 2, 3, and 4, respectively), and this production was n ot influenced (P > 0.05) by the various treatments. In contrast, IGF-I prod uction by granulosa cells (2.0 to 6.2 ng per 100,000 cells per 24 h) was in fluenced by treatment in Exp. 1, 3, and 4 and was greater than IGF-I produc tion by thecal cells (Exp. 2, 3, and 4). Alone, insulin, FSH, LH, and corti sol (but not estradiol) each decreased (P < 0.05) granulosa-cell IGF-I prod uction by 20 to 57%; combined treatments of insulin plus FSH or insulin plu s cortisol decreased IGF-I production to levels seen with insulin alone. Gl ucagon had no effect (P > 0.10) on IGF-I production in the absence or prese nce of insulin. In the presence of insulin, epidermal growth factor, basic fibroblast growth factor, and estradiol decreased (P < 0.05) IGF-I producti on below that observed for insulin alone. These results indicate that, duri ng follicular development in cattle, changes in intrafollicular levels of I GF-I may be due to hormonally-induced changes in granulosa-cell, but not th ecal-cell, IGF-I production.