Insulin effects in clarias batrachus L.: a combined biochemical and anatomical study

The effect of mammalian insulin was studied in a freshwater fish, Clarias batrachus, at both high and low ambient temperatures. The hormone produced a significant but delayed, yet recoverable, lowering of blood glucose, a concurrent decrease in liver glycogen, and an increase in the glycogen content of muscles. The decrease in brain glycogen occurred during advanced hypoglycemia. Hypoglycemic seizures developed intermittently in most of the fishes whose plasma glucose and brain glycogen levels had been considerably depleted. Necrobiotic changes in the pancreatic islets, including degranulation and atrophy, and necrosis of B cells, were seen in the treated fish. In some cases damage to A cells and the acinar tissue was also observed. With the restitution of normal glucose and glycogen values, the islet cells also seemed to have recuperated. Changes in glycemia, glycogen, and the islets were more pronounced in the fishes held at 24 degrees C than in those at 10 degrees C, indicating that the ambient temperature plays an important role in blood glucose homeostasis as well as insulin.