THE EFFECTS OF INSULIN IGF-I ON GLUCOSE AND LEUCINE METABOLISM IN THEREDCLAW CRAYFISH (CHERAX-QUADRICARINATUS)/

In recent years, invertebrate peptides have been identified which shar e substantial homologies with vertebrate insulin and insulin-like grow th factors (IGFs), indicating a high degree of conservation of insulin /IGF systems through animal evolution. In a previous study, we provide d evidence for the presence of IGF-I-like peptides in the redclaw (Che rax quadricarinatus), a species of freshwater crayfish endemic to nort hern Australia river systems which has attained support as a culture s pecies. The general aim of the current study was to elucidate the func tional significance of IGF-I-like peptides in this species by examinin g the effects of mammalian IGF-I on glucose and leucine metabolism. ju venile redclaw were injected with a single dose of purified human insu lin, recombinant human (rh) IGF-I, or Des-1-3-IGF-I. Glucose levels in redclaw tissues were then determined over an 8-hr period using enzyma tic approaches. It was shown that injection of rhIGF-I induced an acut e increase in free glucose content in hepatopancreas while Des-1-3-IGF -I and insulin raised free glucose levels in abdominal muscle. Radiola bel tracer approaches also demonstrated that injection of rhIGF-I incr eased glycogen synthesis in abdominal muscle and elevated the incorpor ation of leucine into protein in both abdominal muscle and hepatopancr eas. Taken together, the findings of this study suggest that IGF-I-lik e peptides are biologically active in this species and may be of signi ficance to metabolic and growth-related processes. (C) 1997 Academic P ress.