THE ACTION OF INSULIN AND OF ANTERIOR PITUITARY EXTRACT IN NORMAL AND HYPOPHYSECTOMIZED RATS

Abstract

In normal and hypophysectomized rats, both fasted and fed, detns. were made of liver and muscle glycogen and blood sugar, of the absorption rates of the fed glucose, of the R.Q. and metabolic rates following treatment with insulin and with ant. pituitary extract given with insulin. Fasted hypophysectomized rats required about 1/30 the dose that produced the same hypoglycaemic effects in normal rats. Adrenal-demedullation increased the sensitivity of otherwise normal rats but to a much smaller extent. 0.05 or 0.01 unit of insulin per kg. profoundly reduced the rates of O consumption of hypophysectomized rats, a reduction not correlated with critical reduction of blood sugar levels in a variety of exptl. conditions. When fed glucose after fasting, hypophysectomized rats were only moderately more sensitive to insulin; there was little change in the rate of glucose oxidation but a marked reduction in the rate of utilization of non-carbohydrate material. In normal rats similarly treated, the only observed effect was increased deposition of muscle glycogen at the expense of liver glycogen and blood glucose. An alkaline extract of ant. pituitary, in both normal and hypophysectomized rats, prevented all the effects of insulin but was not hyperglycemic when given alone nor did it prevent the spontaneous hypo-glycemia in fasted hypophysectomized rats; but in fed animals, it depressed the R.Q.s and favored deposition of muscle glycogen (in the latter respect producing the same result as insulin, but necessarily by a different path). The contra-insulin effects of the ant. pituitary extracts are perhaps best explained as due in part to the prevention of deposition of muscle glycogen from blood sugar, and in part to depression of carbohydrate oxidation.