INFLUENCE OF THE DIETARY POTASSIUM INTAKE ON THE NATRIURETIC EFFECT OF HYDROCHLOROTHIAZIDE IN RATS

  • 1 January 1982
    • journal article
    • research article
    • Vol. 220  (1) , 178-182
Abstract
Hydrochlorothiazide (HCTZ)-induced Na requirement was examined in rats fed a standard diet containing 250 mg of HCTZ/kg food and given a free choice between H2O and 0.46 M NaCl. HCTZ treatment led to a persistent 8-fold increase of NaCl intake. An increase of the K content of the food from 100 to 600 mmol/kg reduced the NaCl intake by 75%. Maintenance on a high K diet prevented the HCTZ-induced requirement for extra Na and diminished HCTZ-induced loss of body weight and urinary Na loss. Determinations of Li clearance (CLi) in unanesthetized rats by using nontoxic doses of Li was used as a measure of Na clearance at the end of the proximal tubules (CNa prox). The urinary Na+ clearance divided by the urinary Li clearance (CNa/CLi) was used to express the fractional escape of Na from distal reabsorption. In HCTZ-treated rats, maintenance on a high K diet reduced CNa and CNa/CLi. A high K intake increased CNa prox, but this effect was least in HCTZ-treated rats. A high K intake reduced the natriuretic effect of HCTZ. The renal mechanism is presumably a K+-induced compensatory increase of the reabsorption of Na delivered from the proximal tubules.

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