Respiratory Effects of Carbonic Anhydrase Inhibition in the Trained Unanesthetized Dog

¹ From the Department of Physiology-Biophysics, School of Aviation Medicine, USAF, Randolph Air Force Base, Texas

Experimental studies are described in which trained unanesthetized dogs were given a single intravenous injection of 2-acetyl-amino-1,3,4-thiadiazole-5-sulfonamide, a carbonic anhydrase inhibitor. Effects on pulmonary ventilation, alveolar gas exchange, arterial blood gas tensions and arterial blood pH were observed. The drug produced a state of hyperventilation associated with a rise in the alveolar-arterial Po₂, a fall in alveolar Pco₂, a diuresis of alkaline urine and a state of acidosis probably due to CO₂ retention and urinary loss of cations. No changes in metabolic rate or the alveolar exchange ratio were noted. Theoretical calculations, made to estimate the pH and Pco₂ of the pulmonary capillary blood, indicated that the latter becomes relatively alkaline following injection of the drug.