Laboratory Investigation

Kidney International (1981) 20, 643–648; doi:10.1038/ki.1981.188

Studies on the mechanism whereby acidemia stimulates collecting duct hydrogen ion secretion in vivo

André Gougoux, Patrick Vinay, Guy Lemieux, Maria-Angelica Duran, Ching-Bun Chen, Marc B Goldstein, Bobby J Stinebaugh, Siu-Cheung Tam and Mitchell L Halperin

Renal Divisions, Universities of Montreal and Toronto, Canada and Baylor College of Medicine, Houston, Texas

Correspondence: Dr M L Halperin, Lab #1, Research Wing, St. Michael's Hospital, 38 Shuter Street Annex, Toronto, Ontario, Canada, M5B 1A6

Received 5 November 1980; Revised 4 March 1981.

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Abstract

Studies on the mechanism whereby acidemia stimulates collecting duct hydrogen ion secretion in vivo. The purpose of these studies was to elucidate the mechanism whereby collecting duct hydrogen ion secretion was augmented by acidemia. The urine minus blood PCO2 difference in alkaline urine (U-B PCO2) was used to evaluate this parameter. In dogs with a normal ECF volume, the U-B PCO2 was high, and there was no significant relationship between the U-B PCO2 factored for the urine bicarbonate concentration and the blood hydrogen ion concentrations unless amiloride, an agent that abolishes the transtubular potential difference, was present. In this latter case, the U-B PCO2 was a linear function of the urine bicarbonate concentration, and the U-B PCO2 factored for the urine bicarbonate concentration was directly proportional to the blood hydrogen ion concentration. To extend the pH range considerably, we used lysine to induce bicarbonaturia in dogs with an expanded ECF volume. Amiloride now caused only a small decrease in the U-B PCO2 at any urine bicarbonate concentration, and furthermore, it did not influence the linear relationship between the U-B PCO2 factored for the urine bicarbonate concentration and the blood hydrogen ion concentration. These results suggest that acidemia stimulates collecting duct hydrogen ion secretion by a mechanism that appears to be independent of the amiloride-sensitive component of the U-B PCO2. We speculate that the mechanism might involve an increased intracellular hydrogen ion concentration during acidemia.

Etude du mécanisme par lequel l'acidémie stimule la sécrétion d'ion hydrogène par le canal collecteur in vivo. Le but de ce travail est d'élucider le mécanisme par lequel la sécrétion d'ion hydrogène est augmentée par l'acidémie. La différence urine-sang de PCO2 en urine alcaline (U-B PCO2) a été utilisée pour évaluer ce paramètre. Chez des chiens avec un volume extracellulaire (ECF) normal, la différence U-B PCO2 est élevée et il n'y a pas de relation significative entre cette différence rapportée à la concentration urinaire de bicarbonate et la concentration sanguine d'ion hydrogène sauf quand de l'amiloride, un agent qui abolit la différence de potentiel transtubulaire, est administré. Dans ce cas la différence U-B PCO2 est une fonction linéaire de la concentration urinaire de bicarbonate et U-B PCO2 rapportée à la concentration de bicarbonate urinaire est directement proportionnelle à la concentration sanguine d'ion hydrogène. Afin d'étendre considérablement l'éventail de pH la lysine a été employée pour déterminer une bicarbonaturie chez le chien dont le volume extracellulaire est augmenté. Dans cette situation, l'amiloride ne détermine qu'une faible diminution de U-B PCO2 à n'importe quelle concentration urinaire de bicarbonate, et, de plus, il n'influence pas la relation linéaire entre U-B PCO2 rapportée à la concentration de bicarbonate urinaire et la concentration sanguine d'ion hydrogène. Ces résultats suggèrent que l'acidémie stimule la sécrétion d'ion hydrogène par le canal collecteur par un mécanisme qui parait indépendant de la composante sensible à l'amiloride de U-B PCO2. Nous faisons l'hypothèse que ce mécanisme peut impliquer une augmentation de la concentration intracellulaire d'ion hydrogène au cours de l'acidémie.

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