THE RÔLE OF THE ANTERIOR PITUITARY IN THE MAINTENANCE OF NORMAL BLOOD SUGAR LEVELS AND IN THE PHYSIOLOGICAL MOBILIZATION OF LIVER GLYCOGEN

Abstract

In earlier work it was shown that intravenously infused adrenaline produces only a slight hyperglycemic response in hypophysectomized dogs in contrast to the marked hyperglycemia it produces in normals. This phenomenon is not due to lack of liver glycogen since all the hypophysectomized dogs had amts. of liver glycogen which if present in normal dogs would have been sufficient to have produced a marked hyperglycemia. Thus in the absence of the ant. pituitary there is an impairment in the mobilization of liver glycogen stores by infused adrenaline. The present study showed that the liver glycogen of hypophysectomized dogs was also resistant to adrenaline secreted under physiological conditions as well as to other glycogenolytic agents which may function normally. It was found that within 2 daya following hypophysectomy the post-absorptive blood sugar of dogs fell to a level considerably below its pre-operative value, to which it never returned. In the succeeding wks. the post-absorptive blood sugar fluctuated widely around the lower level with a tendency to fall further rather than to rise. Coexisting with these markedly low post-absorptive blood sugar levels all the hypophysectomized dogs had liver glycogen stores which if present in normal dogs would have been sufficient to have maintained normal blood sugar levels. The markedly low blood sugar levels of the hypophysectomized dogs must have called forth adrenaline and other glycogenolytic agents. Since none of these was effective in raising the blood sugar, despite the adequate liver glycogen stores., it is concluded that in the absence of the ant. pituitary there is an impairment in the mobilization of liver glycogen by physiological agents normally effective, and that this impairment is in part responsible for the characteristically low post-absorptive blood sugar levels of hypophysectomized dogs.