EFFECT OF LOW AND HIGH POTASSIUM DIETS ON H-K+-ATPASE AND NA+-K+-ATPASE ACTIVITIES IN THE RAT INNER MEDULLARY COLLECTING DUCT CELLS()

This study was designed to measure H-K-ATPase and Na-K-ATPase activiti es in rat inner medullary collecting duct (IMCD) cells during potassiu m depletion and loading. Both enzyme activities were similarly distrib uted from the proximal to the distal portion of this nephron segment. One week K depletion did not stimulate H-K-ATPase activity but reduced Na-K-ATPase activity. Within 2 weeks after the onset of potassium dep letion, the rats developed metabolic alkalosis, and H-K-ATPase activit y was suppressed while Na-K-ATPase activity had returned to control va lues. H-K-ATPase activity was suppressed following potassium loading w hereas Na-K-ATPase activity was unchanged. The results are consistent with the presence of H-K-ATPase in IMCD and indicate that H-K-ATPase a nd Na-K-ATPase activities are modulated by potassium intake.