The Effects of Glucocorticoids (Dexamethasone) on Insulin-Like Growth Factor-I,IGF-Binding Proteins,and Growth in Chickens

Abstract

The effect of glucocorticoids (dexamethasone) on circulating concentrations of insulin-like growth factor (IGF)-I and IGF binding proteins (IGFBPs) was examined in young (2-week-old) chickens. Increasing dosages (6, 60, and 600 μg/kg) of dexamethasone resulted in progressive growth retardation as evidenced by decreased body-weight gain, reduced bone growth, and breast muscle weights, together with immunosuppression as indicated by decreased thymus and bursa weights. Plasma concentrations of IGF-I were progressively reduced with increased doses of dexamethasone. There were no changes in circulating IGFBPs except on Day 7 when binding activity of the 36-kDa IGFBP was increased by dexamethasone (6 μg/kg). It is speculated that similarities exist between the 36-kDa IGFBP and the mammalian IGFBP-1 based on the response to dexamethasone treatment.