EFFECTS OF HORMONES ON GLUCOSE UTILIZATION IN FASTED RATS1

Abstract

The permeability of tissues toward glucose was explored in rats under various hormonal and environmental influenees. The velocity constant K expressing the rate of disappearance of glucose from blood after rapid intravenous injection of a small load of glucose was critically analyzed as an index of glucose utilization. Acute treatments with large doses of glucagon and hydrocortisone led only to negligible effects on K. One hour after epinephrine injection, the persisting hyperglycemia appeared to be due more to increased liver glycogenolysis than to inhibition of glucose utilization. A marked enhancement of K developed 2 hours after a moderate dose. As expected, severe insulin hypoglycemia was accompanied by a sharp increase in K; this was followed by a drastic decrease during the restoration to normal of the blood glucose level. A single injection of thyroxin led to a rapid increase in K and to a small degree of hyperglycemia. After pretreatment of the animals with thyroxine, the moderate hyperglycemia persisted but K returned to normal. Rats exposed to 5[degree]C for 4 hours exhibited a small decrease in K. When cold exposure was prolonged for 14 days, an inverse reaction was noted, together with marked insulin hypersensitivity.