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Effects of gonadotropins and insulin-like growth factor-I (IGF-I) and IGF-II on steroid production by bovine granulosa cells in vitro

University of British Columbia

A serum-free culture system for bovine granulosa cells was developed. Effects of follicle-stimulating hormone (FSH), luteinizing hormone (LH), insulin-like growth factor-I (IGF-I), and insulin-like growth factor-II (IGF-II) on steroid production by bovine granulosa cells were determined. Bovine granulosa cells from small (< 5 mm), medium (6-10 mm), and large (>10 mm) follicles were cultured for 48 h. Concentrations of estradiol-17p (E₂) and progesterone (P₄) were measured by radioimmunoassay. For granulosa cells from all classes of follicles, the basal E₂ production was high during day 1 culture. With time of culture, E₂ production decreased dramatically in granulosa cells from all classes of follicles. Estradiol-17ß production increased significantly with increasing follicle size (p < 0.01). Basal P₄ production increased with the time of culture and with increasing follicle size (p < 0.01). These results indicated that a serum-free culture system can support basal granulosa cell steroidogenesis and can be used to study the effects of FSH, LH, IGF-I, and IGF-II on bovine granulosa cell steroidogenesis. Only a low dose of FSH (1 ng/ml) stimulated E 2 production by granulosa cells from medium and large follicles (p < 0.05); high doses of FSH (10, 100 ng/ml) inhibited E₂ production by granulosa cells from large follicles (p < 0.05). Follicle-stimulating hormone stimulated P₄ production from granulosa cells of all classes of follicles (p < 0.05). Luteinizing hormone inhibited E₂ production in medium and large follicles (p < 0.05). Luteinizing hormone increased P₄ production in medium and large follicles (p < 0.05). A high dose of IGF-I (100 ng/ml) increased E₂ production by granulosa cells from medium and large follicles (p < 0.05). Insulin-like growth factor-I increased P₄ production from all categories of follicles. Estradiol-170 production from large follicles decreased in response to IGF-II (10, 100, 500 ng/ml; p < 0.05). A dose of IGF-II (500 ng/ml) inhibited E₂ production by granulosa cells from medium follicles. Insulin-like growth factor-II inhibited P₄ production by granulosa cells from medium and large follicles (p < 0.05). Progsterone production from small follicles was inhibited only at a high dose of IGF-II (500 ng/ml; p < 0.05). In conclusion, FSH, LH, IGF-I, and IGF-II have significant effects on steroid production by bovine granulosa cells from small, medium, and large follicles in culture. The bovine granulosa cell culture system developed in the present study can be used for the further studying the effects of hormones, growth factors and their interactions on bovine granulosa cells.

Thesis/Dissertation

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2009-02-16

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http://hdl.handle.net/2429/4622

Animal Science

University of British Columbia

UBCV

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