Inhibition of sodium transport by hyperbaric oxygen in the toad urinary bladder

In the isolated toad bladder, 2--10 ATA of oxygen reversibly inhibited the active transport of sodium ions across the bladder, measured as the short-circuit current. Extent of inhibition was dependent on the oxygen pressure and length of exposure. Oxygen at 1 ATA had no effect on sodium transport for up to 2 days of exposure. However, bladders exposed for 18 h to oxygen at 1 ATA were more sensitive to a subsequent exposure to hyperbaric oxygen. The hormonal stimulation of sodium transport by pitressin or aldosterone was inhibited by hyperbaric oxygen but was unaffected by prolonged exposure to oxygen at 1 ATA. Incubation of bladders with aldosterone or sodium pyruvate increased the sensitivity of sodium transport to the inhibitory effects of hyperbaric oxygen. The mechanism of the inhibition of sodium transport in the toad bladder by hyperbaric oxygen was not known.