Effects of beta-hydroxybutyrate, glycerol, and free fatty acid infusions on glucagon and epinephrine secretion in dogs during acute hypoglycemia.

The importance of glucagon in the regulation of carbohydrate metabolism is clearly established. However, the role played by this hormone in the regulation of the overall fuel economy is less certain, particularly with respect to such nonglucose fuels as free fatty acids, glycerol, and ketoacids. In order to elucidate glucagon's role with respect to the latter substrates, dogs were infused with solutions of these three fuels, and their A-cell responses to concomitant insulin-induced hypoglycemia were studied. In addition, epinephrine levels were also monitored. It was found that while these infusions failed to suppress glucagon release, the ketoacid infusion did significantly reduce epinephrine secretion during the insulin-induced hypoglycemic period. It was therefore concluded that glucagon secretion under these experimental conditions is not responsive to prevailing non-glucose fuel levels. Indeed, these data suggest that the sympathetic nervous system may play an important role in the regulation of the over-all fuel economy.