ROLE OF SODIUM‐POTASSIUM ATPASE IN PHOSPHATE TRANSPORT BY THE EVERTED SACS OF MOUSE INTESTINE

1. This study investigated the uptake and release of phosphate from everted intestinal sacs of mice. 2. When the activity of sodium-potassium ATPase was altered (by changing the cationic concentrations in the medium by the addition of ouabain and the manipulation of metabolism by the use of selective inhibitors or stimulants), the release of phosphate appeared to be much more affected by the changes than the uptake of phosphate. 3. A small sodium gradient allowed uptake to be maintained. The addition of ouabain in the presence of an attenuated gradient significantly reduced the uptake and release of phosphate. The inhibitory effect of ouabain on phosphate release was partly reversed by an increase in the potassium concentration in serosal fluid. 4. These results indicate a role for sodium-potassium ATPase in phosphate release from the intestine.