Interrelationships of sodium transport and carbon dioxide production by the toad bladder: Response to changes in mucosal sodium concentration,to vasopressin and to availability of metabolic substrate

Summary Active sodium transport and CO₂ production were measured simultaneously in toad bladders mounted in membrane chambers. The rate of sodium transport was varied by changing the concentration of sodium in the mucosal bath (substitution with choline), by adding vasopressin, by adding metabolic substrates and by adding malonate, and the ratio of the change of sodium transport and CO₂ production was determined Mean values for Na/CO₂ (equiv/mole) were: Nacholine 18.3±1.1; vasopressin 15.5±2.8; and pyruvate (corrected for the increment in nontransport CO₂) 15.4±3.5. Based on previously determined values for the respiratory quotient (R.Q.), calculated mean values for Na/O₂ ranged between 15.5 and 18.5 equiv/mole. It appears that basal metabolism does not contribute to metabolism supporting sodium transport when the rate of sodium transport is varied. Transport metabolism appears much more responsive to changes in the availability of endogenous and exogenous substrates than does nontransport metabolism. We conclude that transport and nontransport metabolism are functionally separated in the toad bladder.These results were presented in part at the Annual Meeting of the American Society of Nephrology, November 1973.