Biol Reprod Keystone Symposia Conference on Frontiers in Reproductive Biology & Regulation of Fertility.
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Biology of Reproduction, Vol 54, 255-263, Copyright © 1996 by Society for the Study of Reproduction

ARTICLES

Interactions among basic fibroblast growth factor, epidermal growth factor, insulin, and insulin-like growth factor-I (IGF-I) on cell numbers and steroidogenesis of bovine thecal cells: role of IGF-I receptors

LJ Spicer and RE Stewart
Department of Animal Science, Oklahoma State University, Stillwater 74078, USA.

The objectives of the present study were to determine the interaction among basic fibroblast growth factor (bFGF), epidermal growth factor (EGF), insulin, and insulin-like growth factor-I (IGF-I) on cell numbers, steroidogenesis, and IGF-I binding sites in cultured thecal cells. Cells from large (> or = 8 mm) follicles were collected from cattle and cultured for 4 days. Treatment with 1-30 ng/ml of bFGF for 2 days increased (p < 0.05) thecal cell numbers but inhibited (p < 0.05) androstenedione and progesterone production in the presence of insulin alone or insulin plus LH. Treatment with 1-30 ng/ml of bFGF for 2 days also inhibited (p < 0.05) the number of specific 125I-IGF-I binding sites in thecal cells, with maximal inhibition being detected at 1 ng/ml; coculture with 100 ng/ml LH did not influence this effect. In the absence of bFGF and the presence of LH, 30 ng/ml of IGF-I increased thecal cell numbers and production of androstenedione and progesterone. However, cotreatment with 10 ng/ml bFGF inhibited thecal cell response to IGF-I. Cotreatment consisting of 3-100 ng/ml EGF with insulin increased (p < 0.05) thecal cell numbers but decreased (p < 0.05) androstenedione and progesterone production and the number of specific 125I-IGF-I binding sites in thecal cells, with maximal inhibition observed at 3 ng/ml of EGF. Also, cotreatment consisting of 3 and 10 ng/ml of EGF with IGF-I plus LH inhibited (p < 0.05) cell numbers and production of androstenedione and progesterone by thecal cells. These results suggest that bFGF, EGF, insulin, and IGF-I may interact to play a significant role in basal and LH-modulated thecal cell steroidogenesis and mitogenesis during follicular development in cattle.




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Copyright © 1996 by the Society for the Study of Reproduction.