Influence of insulin on follicular development and the intrafollicular insulin-like growth factor I (IGF-I) system in sows after weaning

Journal of Reproduction and Fertility
N C WhitleyN M Cox

Abstract

Twenty-four crossbred primiparous sows were used to investigate the influence of insulin administration after weaning on the intrafollicular insulin-like growth factor i (IGF-I) system. Sows received 0.4 i.u. insulin kg-1 bodyweight or an equivalent volume of saline for 3 days (n = 5 insulin; n = 4 saline) or 5 days (n = 5 insulin; n = 6 saline) after weaning or served as untreated controls on day 1 (n = 4). The number and diameters of ovarian follicles were recorded, and fluid was aspirated from the 20 largest follicles for determination of oestradiol and IGF-I by radioimmunoassay and of insulin-like growth factor-binding proteins (IGFBPs) by western ligand blotting. The walls of the follicles were collected for mRNA analysis by RNase protection assay or granulosa cells were collected for estimation of apoptosis by flow cytometry. Insulin treatment resulted in smaller diameters of all follicles (P < 0.05) and tended (P < 0.07) to increase the number of follicles available on day 5 compared with saline-treated animals (19.8 versus 17.8). The concentration of oestradiol in follicular fluid from large (7-10 mm) follicles on days 3 and 5 was reduced (treatment by size class interaction; P < 0.05) by insulin treatment. Insulin also...Continue Reading

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