Effect of Pancreatectomy on the Adrenal Medullary Response to Hypoglycemia in the Dog

Abstract

The effect of hypoglycemia induced by the injection of glucagon-free insulin on adrenal medullary secretion was studied in 4 totally pancreatectomized dogs and in 3 sham-pancreatectomized controls. There was a clear-cut statistically significant increase in the output of catecholamines in the pancreatectomized animals, although the mean increase was less than it was in the shamoperated dogs. It is concluded that glucagon from the pancreas is not an obligatory mediator of the adrenal medullary response to hypoglycemia in the dog. (Endocrinology 74: 656, 1964) V ON EULER and his associates (1) andSarcione et al.(2) have suggested that the increase in adrenal medullary secretion produced by hypoglycemia may not be due to the depression in blood sugar per se. Because hypoglycemia is a stimulus for the release of glucagon (3) and glucagon stimulates the adrenal medulla by a direct action on medullary cells (2, 4-6), Sarcione et al. postulated that the adrenal medullary response to hypoglycemia was caused by the increase in circulating glucagon. To test this hypothesis, we determined the effect of pancreatectomy on the adrenal medullary response to hypoglycemia induced in dogs by the injection of glucagon-free insulin. Materials and MethodsSeven 10.2-18.2 kg male mongrel dogs which had been fasted for 48 hr were studied. Each was anesthetized with pentobarbital, and the pancreas was exposed through a right rectus incision. In 4 dogs the pancreas was removed, whereas in the remaining 3 it was left in place (shampancreatectomy controls). The wounds were then sutured, and in each dog the right lumboadrenal vein was cannulated through a flank incision by the method of Hume and Nelson (7). Cannulas were also placed in one femoral artery for collecting blood and monitoring blood pressure and in one femoral vein for administering blood and insulin.Arterial and adrenal venous blood collections were begun 1 hr or more after cannulation of the lumboadrenal vein and from 3 to 4^ hr after pancreatectomy or sham-pancreatectomy. Collections were made 15 and 5 min before and 15,