Studies on the Pathogenesis of Type I (Distal) Renal Tubular Acidosis as Revealed by the Urinary <sc>Pco</sc><sub>2</sub> Tensions

M. L. Halperin; M. B. Goldstein; A. Haig; M. D. Johnson; B. J. Stinebaugh

doi:10.1172/JCI107604

Studies on the Pathogenesis of Type I (Distal) Renal Tubular Acidosis as Revealed by the Urinary Pco₂ Tensions

Published March 1, 1974 - More info

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Abstract

This study was designed to investigate the pathogenesis of type I (distal) renal tubular acidosis.

Urinary and blood Pco₂ tensions were determined when the pH of the urine was equal to or exceeded the corresponding blood pH. This provided an indication of net hydrogen ion secretion in the distal nephron. In 16 normal subjects, the Pco₂ of the urine exceeded blood values (U-B Pco₂) by 32.7±3.1 mm Hg. In contrast, the urinary Pco₂ tensions in 10 patients with type I (distal) renal tubular acidosis were not significantly greater than blood values (U-B Pco₂ = 2.0±2.2 mm Hg). These results indicate that type I (distal) renal tubular acidosis is caused by failure of the cells of the distal nephron to secrete hydrogen ions rather than to gradient-limited hydrogen ion addition to the urine. This is suggested by the fact that urinary Pco₂ levels should be higher than blood Pco₂ levels when hydrogen ions are secreted into urine containing bicarbonate in the distal nephron and they were not in this study despite the presence of a favorable hydrogen ion gradient (tubular fluid pH exceeded blood pH).