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Effects of KCl infusions on proximal tubular function in normal and potassium-depleted rats

1973; Elsevier BV; Volume: 4; Issue: 5 Linguagem: Inglês

10.1038/ki.1973.123

1523-1755

David Z. Levine, Teena Walker, Lorena A. Nash, S. Raman,

Electrolyte and hormonal disorders

Effects of KCl infusions on proximal tubular function in normal and potassium-depleted rats. In order to extend reports indicating that potassium loading inhibits proximal tubular water reabsorption and that potassium depletion causes enhanced proximal bicarbonate reabsorption, experiments were carried out on normal rats and on rats depleted of potassium by dietary means alone. Dietary variables other than potassium were not present in our studies. Despite significant potassium depletion, metabolic alkalosis was not present in the potassium-restricted group. Isotonic KCl infusions in normal animals suppressed proximal tubular water reabsorption in association with a reduction in the absolute net reabsorptive rate for bicarbonate. In contrast, isotonic KCl infusions in potassium-depleted animals did not alter absolute bicarbonate or water reabsorption by proximal tubules. Although fractional bicarbonate reabsorption was higher in normal rats than in potassium-depleted animals, we were unable to show a statistically significant increase in the absolute reabsorptive rate for bicarbonate. However, fractional bicarbonate reabsorption fell in response to the potassium infusion in both normal and potassium-depleted rats, an effect which occurred in association with decreases in fractional water reabsorption. Effets de l'infusion de KCl sur la fonction tubulaire proximale de rats normaux et depletes en potassium. Des experiences ont ete conduites chez des rats normaux et des rats depletes en potassium, au moyen d'un regime adequat, afin d'accroitre les arguments qui indiquent que la charge en potassium inhibe la reabsorption tubulaire proximale d'eau et que la depletion en potassium determine une augmentation de la reabsorption proximale de bicarbonate. Malgre une depletion en potassium significative l'alcalose metabolique n'a pas apparu dans le groupe restreint en potassium. L'infusion de KCl isotonique aux animaux normaux diminue la reabsorption proximale d'eau en meme temps que diminue le debit net de reabsorption du bicarbonate. Au contraire l'infusion de KCl isotonique aux animaux depletes ne modifie pas la reabsorption absolue d'eau ou de bicarbonate par les tubes proximaux. Bien que la reabsorption fractionnelle de bicarbonate soit plus grande chez les rats normaux que chez les animaux depletes, il nous a ete impossible de mettre en evidence une augmentation significative du debit de reabsorption absolue de bicarbonate. La reabsorption fractionnelle de bicarbonate, cependant, diminue en reponse a l'infusion de potassium a la fois chez les rats normaux et chez les rats depletes, effet qui survient en association avec des diminutions de la reabsorption fractionnelle d'eau.