Insulin and glucagon: plasma levels and pancreatic release in the genetically obese Zucker rat.

Circulating levels of insulin and glucagon, as well as their release from isolated pancreatic islets, have been measured in Zucker rats to examine the effect of genotype, sex and diet. The obese animals had higher plasma insulin levels and enhanced release from islets when compared to lean controls. Conversely, obese animals, despite no significant differences in fed plasma levels of glucagon, showed substantially reduced release from islets. Diet had no main effect on any of these parameters.