Quantification of total insulin-like growth factor (IGF-1) in rat tissues

Abstract

Total IGF-I in some tissues (liver, kidney, heart, lung, thymus, spleen and skeletal muscle) from normal adult rats was measured by specific radioimmunoassay (RIA). Acid-ethanol extraction (AE), currently utilised to separate IGF-I binding proteins (IGFBPs) in serum prior to RIA, was assessed in tissue analysis and was compared with AE followed by crioprecipitation. It was found that AE extraction does not completely remove IGFBPs, whereas the additional crioprecipitation step releases approximately 20% more IGF-I from the tissues. Rat IGF-I tissue distribution was finally established by RIA. The method here described is useful for the study of the metabolic or nutritional IGF-I regulation