Renal memory after potassium adaptation: role of Na+-K+-ATPase
1Department of Medicine, Northwestern University Medical School, Chicago, Illinois.
Abstract:
The present study was designed to explore the time course of the resolution of enhanced Na+-K+-ATPase activity in the cortical collecting tubule (CCT) and the parallel changes in renal K excretion that are characteristic of potassium adaptation. Potassium-adapted male Sprague-Dawley rats manifested an enhanced kaliuretic response to an acute intravenous load of KCl and a doubling of Na+-K+-ATPase activity in the CCT. Withdrawal of dietary K loading from these adapted rats was associated with a gradual resolution of these adaptive biochemical (t1/2 of Na+-K+-ATPase return to base line 48 h) and excretory changes. During this resolution phase, however, a temporal discrepancy was uncovered between the change in dietary K and the slower changes in enzyme activity and renal K excretion with a persistence of the enhanced kaliuresis leading to a negative K balance. We conclude that the slow inactivation, after withdrawal of K loading, of the increased membrane transport proteins of K adaptation, will manifest as a renal memory of the antecedent excretory requirements.
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