Na-K-ATPase and transepithelial sodium transport in the toad

Abstract

1. 1. Studies have been conducted using the isolated toad skin and urinary bladder preparations in an attempt to evaluate the relationship between sodium, potassium activated adenosinetriphosphatase (Na-K-ATPase) system and transepithelial sodium transport. 2. 2. In both the skin and bladder, ouabain showed no significant inhibitory effect on the Na-K-ATPase activity at 23°C, while it exerted a potent inhibition of the active sodium transport at this temperature. On the other hand, at 37°C, both the Na-K-ATPase activity and the sodium transport were strongly inhibited by the glycoside. 3. 3. The inhibitory effect of ouabain on the sodium transport was reduced as potassium concentration in the serosal bathing medium was increased. 4. 4. There was no apparent correlation between the magnitude of sodium transport and the Na-K-ATPase activity of the skin regardless of whether the skin was treated with vasopressin (ADH), ouabain, or both ADH and ouabain. 5. 5. These results emphasize the difficulty associated with correlating sodium transport across epithelia with activity of Na-K-ATPase in a subcellular fraction.