Effects of Insulin, Insulin-Like Growth Factor I, and Gonadotropins on Bovine Granulosa Cell Proliferation, Progesterone Production, Estradiol Production, and(or) Insulin-Like Growth Factor I Production In Vitro

The objectives of the present studies by severalfold on d 4. In cells from both sizes of were to determine the effect of insulin, insulin-like follicles, insulin (1 pg/mL), in the presence of FSH, growth factor I (IGF-I), testosterone, and FSH on increased estradiol production per cell. In contrast, proliferation, progesterone production, and(or) esIGF-I (100 ng/mL) inhibited estradiol production by tradiol production of bovine granulosa cells. In addicells from small follicles and stimulated estradiol tion, existence of IGF-I mRNA in granulosa cells and production by cells from large follicles. Insulin-like in vitro IGF-I production by granulosa cells were growth factor I1 (100 ng/mL) and insulin at higher assessed. Cells from small (1 to 5 mm) and large ( 2 8 doses ( 2 5 gg/mL) had no effect on estradiol producmm) follicles were collected from cattle and cultured tion by cells from small and large follicles. Granulosa for either 3 or 4 d. When cells from small follicles were cells contained four IGF-I mRNA transcripts and cultured, insulin ( . l to 10 pg/mL) and IGF-I (100 to produced IGF-I in vitro. These results support the 400 ng/mL) increased ( P c .05) cell numbers comhypothesis that insulin and IGF-I may have direct pared with controls. Insulin alone or IGF-I alone local effects on bovine ovarian function, and that these increased ( P < .05) progesterone production per cell effects are influenced by dose and size of follicle.