STUDIES OF ANTERIOR PITUITARY TISSUE IN VITRO: EFFECTS OF INSULIN AND EXPERIMENTAL DIABETES MELLITUS UPON CARBOHYDRATE METABOLISM*

Abstract

Pathways of carbohydrate metabolism have been examined in surviving preparations of normal calf and rat anterior pituitary. Mechanisms for active glycogen turnover and glucose oxidation via the hexose-monophosphate shunt in vitro have been demonstrated. Anterior pituitaries from both species responded to the direct addition of insulin to the suspending media. Micro-methods have been developed for incubation of single rat anterior pituitaries. With this technique, it has been demonstrated that hypophyseal carbohydrate metabolism is significantly reduced in anterior pituitaries excised from rats rendered acutely insulin-deficient by total pancreatectomy or chronically diabetic by alloxanization. The phenomenon could not be attributed to such systemic manifestations of insulin deprivation as ketoacidosis and could not be duplicated by comparable degrees of surgical trauma in animals in which pancreatic function was preserved. The derangement of hypophyseal glucose utilization in rats with experimental diabetes could be prevented or reversed by treatment with replacement quantities of insulin in vivo. The data indicate that the anterior pituitary is responsive to insulin and that intrahypophyseal carbohydrate metabolism in the intact animal may be conditioned by the availability of insulin.