NORMAL DEXTROSE TOLERANCE CURVES, IN THE ABSENCE OF INSULIN, IN HYPOPHYSECTOMIZED-DEPANCREATIZED DOGS

Abstract

Dextrose tolerance tests were performed in completely hypophysectomized-depancreatized dogs, which had not received insulin at any time following the removal of the pancreas (1-8 weeks previously). Normal dextrose tolerance curves were obtained in these animals, in the absence of any known endogenous or exogenous supply of insulin. These results oppose all pre-existing hypotheses concerning the dextrose tolerance curve, which are based either on an insulin-secreting reaction of the pancreas or an activation of previously inert insulin, in reponse to sugar administration. From these and other data it is concluded that the occurrence of the normal dextrose tolerance curve is determined by a homeostatic reaction of the liver whereby this organ decreases its supply of sugar to the blood, in response to the influx of exogenous sugar. In this phenomenon, the rise in the blood sugar may be regarded as the stimulus to the hepatic regulatory mechanism, while the pancreas and hypophysis are opposing influences which determine the blood sugar level or threshold at which the homeostatic reaction comes into play. Clinical and experimental disturbances in carbohydrate metabolism, due to hyper- or hypo-function of the pancreas or hypophysis, are best interpreted as disorders of the above liver mechanism.