Adrenal Cortical Hormone and Ant. Pituitary Extract on Carbohydrate Levels in Fasted Hypophysectomized Rats. ∗

Abstract

Hypophysectomized rats are unable to maintain their carbohydrate stores during fasting as do normal animals. 1 Certain anterior pituitary extracts are capable of preventing completely the changes found in short fasts, such as 8 hours. In longer fasts, however, while muscle glycogen stores are held at normal or supernormal levels, the liver glycogen and blood glucose are not maintained by this treatment. 2 This difference in the response of liver and muscle has led to the suggestion that more than one factor may be concerned in the maintenance of carbohydrate levels in the fasted hypophysectomized rat. 3

Because of the possibility that the adrenal cortex may mediate some of the effects of the anterior pituitary on carbohydrate metabolism, the relationship of the adrenocorticotropic substance of the A. P. and of the adrenal cortical hormones to the factor or factors mentioned above has recently been investigated. That the maintenance of muscle glycogen stores is possible in the absence of the adrenal cortex was early found; 2 and Bennett, working in this laboratory, has recently presented much additional evidence that the factor maintaining muscle glycogen (the “glycostatic” factor) is not the adrenocorticotropic factor. 4 Bennett also showed that adrenocorticotropic preparations on chronic administration (that is, with maintenance or repair of the adrenal cortex) could effect consider all increases in the liver glycogen and blood sugar levels of fasted hypophysectomized rats. 5 From a consideration of these facts, it seemed possible that 2 pituitary factors affecting the carbohydrate stores in these animals were (1) a “glycostatic” substance acting directly on the muscle glycogen, and (2) the adrenocorticotropic hormone affecting also the liver glycogen and thence Mood sugar levels.