INSULIN AND INSULIN-LIKE GROWTH-FACTOR-I IN COHO SALMON ONCORHYNCHUS-KISUTCH INJECTED WITH STREPTOZOTOCIN

Streptozotocin (STR), an agent known to induce damage of pancreatic B cells in mammals, was used to study changes of plasma insulin concentr ation and hepatic insulinlike growth factor I (IGF-I) mRNA levels in j uvenile coho salmon, Oncorhynchus kisutch. Fish were injected intraper itoneally with either 200 mg/kg body wt STR or the vehicle. All fish f ed and grew throughout the experiment; however, the STR-injected fish had lower instantaneous growth rates than control fish (1.4% and 2.1%, correspondingly). Plasma insulin concentration and hepatic IGF-I mRNA levels in STR-treated fish were significantly lower than in the contr ol fish, whereas there was no difference between the two groups of fis h in plasma concentrations of either glucagon or growth hormone. Impai red insulin production caused by STR injection was either coincident w ith or slightly preceded reduction in hepatic IGF-I mRNA expression, i mplying that insulin may affect IGF-I production and, consequently, fi sh growth.