SPRAFKA, J.B.; CHANG, E.S.; SNYDER, M.J.*: Insulin-Like Growth Factor I (IGF-I) Treatment Results in Time- and Dose-Dependent Increases in Tissue Glucose Levels in the Penaeid Shrimp Sicyonia ingentis

Insulin-like growth factors (IGF) are important regulators of vertebrate growth and development. We have previously reported on the identity of IGF-like mRNA in decapod crustacean muscles. The role(s) of IGFs, such as IGF-I, in invertebrate systems remains unclear. In this study, we examined the in vivo effects of IGF-I treatment on glucose levels in Sicyonia ingentis. We show that IGF-I injections promote both dose- and time- dependent increases in abdominal muscle and hepatopancreas glucose levels. Hepatopancreas samples collected 15 min post-IGF-I injection (0.2 MUg/g wet wt.) had mean glucose levels approximately 30% higher than both non-injected and control-injected (0.2 MUg /g wet wt.) shrimp. Glucose levels were still 22% higher 30 min post-injection. Mean glucose levels in abdominal muscle samples 15 min after treatment were unchanged from controls, but at 30 min levels were elevated to 23.2% above controls. Our work demonstrates that IGF-I elicits a distinct metabolic response n this species. The rapid physiological effects suggest that an IGF-like peptide may regulate key metabolic processes in this decapod crustacean. (Funded by NOAA California Sea Grant R/A-108)