Insulin administration in the frog Rana tigrina: studies on the blood glucose and the histology of the endocrine pancreas

Abstract

The effect of various doses of insulin (25-, 50-, and 150 U/kg body weight) on the blood glucose level and islet-cytology of the frog Rana tigrina was studied until 96 h. Following the hormonal administration the frogs exhibited hypoglycemia, abnormal neuromuscular activity and degranulation of both the insulin secreting beta- and glucagon secreting alpha-(alpha2-) cells of the pancreatic islets. The action of insulin was dose and temperature dependent; the higher the dose and temperature, the greater the hypoglycemia and atrophy of islet tissue. The insulin-induced convulsive activity appears to be due to the direct action of this hormone on the nervous system; the shocks are not influenced by thermal variation. The great sensitivity of Rana tigrina to exogenous insulin seems to be related to only a few alpha2-cells in the endocrine pancreas and consequently, a smaller amount of circulating glucagon in this animal.