Pituitary and adrenals are required for hyperglycemic reflex initiated by stimulation of CBR with cyanide

Abstract

We have previously shown that stimulation of carotid body receptors (CBR) with sodium cyanide (NaCN) elicits a rapid hyperglycemic reflex. Here we explore whether the pituitary and adrenals, two glands involved in glucose homeostasis, are necessary for this reflex. Experiments were performed on anesthetized rats that were artificially ventilated. Measurements of hepatic venous-arterial glucose difference indicated that CBR stimulation with a bolus of 5 micrograms/100 g NaCN produced an immediate increase in the output of glucose by the liver. The same dose of NaCN failed to increase hepatic output of glucose in rats with bilateral adrenalectomy or in rats 1 wk after surgical removal of neurohypophysis. Reflex glucose output by the liver was maintained after adenohypophysectomy or in adrenalectomized rats after adrenal autotransplantation to epiploon. Measurements of epinephrine in plasma and in the grafted adrenal tissue showed that the adrenal autograft can store and secrete catecholamines Immunocytochemical observations indicated that the grafted adrenals retain medullary cells. These results indicate that neurohypophysis and adrenals are necessary for the hyperglycemic reflex initiated by CBR stimulation with NaCN and that the participation of these two organs in this reflex is probably humoral.