Mechanism of renal potassium conservation in the rat.

Mechanism of renal potassium conservation in the rat. The mechanisms responsible for renal potassium (K) conservation during dietary potassium deficiency are poorly understood. This study was undertaken to investigate the time course of potassium conservation as well as the roles of distal sodium (Na) delivery, the distal delivery or sodium plus a nonpermeable anion, mineralocorticoid hormone, renal tissue potassium content, and Na-K-ATPase activity in renal potassium conservation. After 72 hours of a low-potassium diet, basal potassium excretion was negligible. After 24 hours, and even more so after 72 hours of potassium restriction, the kaliuretic response to increasing distal delivery of sodium or sodium plus a nonpermeable anion was impaired. After 24 hours of a low-potassium diet, plasma aldosterone levels fell from 180 ± 25 to 32 ± 9 pg/ml (P 42 K microinjection studies of the distal nephron did not suggest any increase in potassium reabsorption. Following 72 hours of diet, potassium reabsorption increased significantly from 26 ± 2% to 41 ± 2% (P Mecanisme de conservation renale du potassium chez le rat. Les mecanismes responsables de la conservation renale du potassium (K) au cours du deficit alimentaire en potassium ne sont pas clairs. Cette etude a ete entreprise pour preciser l'evolution dans le temps de la conservation de potassium et aussi les roles du debit de sodium (Na) distal, du debit distal de sodium, et d'un anion non permeant, des mineralocorticoides, du contenu en potassium du tissu renal et de l'activite de la Na-K-ATPase dans la conservation renale de potassium. Apres 72 heures d'une alimentation pauvre en potassium l'excretion basale de potassium est negligeable. Apres 24 heures, et encore plus apres 72 heures, de restriction de potassium, la reponse kaliuretique a l'augmentation du debit distal de sodium, ou de sodium et d'un anion non permeant, est modifiee. Apres 24 heures de restriction de potassium, la concentration d'aldosterone plasmatique chute de 180 ± 25 a 32 ± 9 pg/ml (P 42 K dans le nephron distal ne suggerent pas d'augmentation de la reabsorption. Apres 72 heures la reabsorption de potassium augmente significativement de 26 ± 2% a 41 ± 2% (P