Mobilization of free fatty acids in dogs during respiratory acidosis

¹ Department of Physiology, Hahnemann Medical College and Hospital, Philadelphia, Pennsylvania

To assay changes in plasma free fatty acids (FFA) during a stress reported to activate a sympathetic discharge, dogs were made hypercapnic by inhaling mixtures of gases containing 15–30% CO₂ in O₂. Results showed that during such a maneuver, plasma FFA and glucose concentrations were elevated. Blood pH and heart rates were decreased and mean blood pressures fell in the early stage of hypercarbia, but gradually rose back to normal within 30 minutes. Dogs with adrenal glands occluded from the circulation showed little or no change in plasma concentrations of FFA or glucose, although blood pH and heart rates declined quantitatively the same as in intact dogs. ‘Adrenalectomized’ dogs were unable to reset lowered blood pressures at pre-CO₂ levels when breathing 30% CO₂. It is concluded that, during the stress of respiratory acidosis, a sympathetic discharge activates a release of adrenal medullary amines, and these in turn raise not only glucose levels, but also FFA, an important energy source.