Studies on a Na + + K +-dependent, ouabain-sensitive adenosine triphosphatase in the avian salt gland

Abstract

1. 1. A Na + + K +-dependent, ouabain-sensitive ATPase was found in homogenates of the avian salt gland. Some of its properties have been investigated. 2. 2. The levels of ouabain-sensitive and ouabain-insensitive ATPase activities were the same in homogenates of tissue from gulls maintained on fresh water and from gulls maintained on 1.5% salt water. 3. 3. The levels of ouabain-sensitive and ouabain-insensitive ATPase activities were the same in homogenates of slices which had been incubated in the absence of acetylcholine and slices which had been incubated in the presence of acetylcholine. (Acetylcholine stimulates NaCl secretion in this tissue.) 4. 4. The oxygen uptake in unstimulated salt-gland slices was reduced about 25% in the presence of 10 −4 M ouabain. The increase in oxygen uptake which occurs in response to acetylcholine did not occur if ouabain was also present. 5. 5. The level of 7-min acid-hydrolyzable phosphate esters in salt-gland slices fell in the presence of acetylcholine but this fall did not occur if ouabain was also present. 6. 6. These results, and the relationship between the rates of Na + transport and ATPase activity in the salt gland, are discussed.