Effect of glucagon on the principal islets of a fresh-water fish, Channa punctatus (Bloch).

Intramuscular administration of crystalline mammalian glucagon (0.5-2.0 mg/kg body weight) evokes significant cytological alterations in the principal islets of Channa punctatus, a fresh-water fish. Initially there is degeneration of the alpha-cells but later the beta-cells are also atrophied. Regressive changes in some of the alpha-cells have been interpreted to reflect their possible role in glucagon secretion. The degeneration of beta-cells appears to be secondary to the fluctuations in the blood glucose level, induced by exogenous glucagon.