THE EFFECT OF EPIDERMAL GROWTH-FACTOR ON CIRCULATING LEVELS OF IGF AND IGF-BINDING PROTEINS IN ADULT GOETTINGEN MINIPIGS

It has recently been demonstrated that epidermal growth factor (EGF) a dministration to neonatal rodents causes growth retardation with conco mitant reductions in circulation levels of IGF-I. We describe the effe cts of systemic EGF administration for 4 weeks on circulating levels o f IGF-I and IGF-binding proteins (IGFBPs) and on thyroid hormones (tri -iodothyronine, T-3; thyroxine, T-4) in sexually mature pig. Goettinge n minipigs of either sex were treated with placebo (n=5) or EGF (30 mu g/kg per day, n=6) s.c. for 4 weeks (in relation to an oesophageal sc lerotherapy regimen). Blood samples were taken under anaesthesia befor e and after 1, 2, 3 and 4 weeks of treatment. Circulating levels of IG F-I, insulin, glucose, T-3 and T-4 were analysed every week and IGFBPs every second week. IGF-I was not reduced significantly after 1 week b ut significantly reduced after 2 and 3 weeks of EGF treatment. A simil ar decline was observed for the major IGFBP, IGFBP-3, which was reduce d after 2 and 4 weeks. IGFBP-1, IGFBP-2 and IGFBP-4 increased througho ut the treatment period (all significantly at week 4). EGF treatment i nduced increased circulating T-3 after 2, 3 and 4 weeks of EGF treatme nt. In conclusion, we report that EGF treatment for 4 weeks in Goettin gen minipigs reduces circulating IGF-I and IGFBP-3, increases circulat ing IGFBP-1, IGFBP-2 and IGFBP-4, and induces a slight hyperthyroidism as judged from increased circulating levels of T-3.