Measurements of pH, Chloride and Inulin Concentrations in Proximal Tubule Fluid of Necturus

To investigate the relationship between chloride concentration and acidification in the proximal tubule of Necturus simultaneous measurements of chloride, inulin and ph were carried out on samples of fluid obtained by micropuncture. The concentration of inulin in tubule fluid always exceeded that of serum, indicating reabsorption of fluid from this part of the nephron. The concentration of chloride in tubule fluid when treated with deproteinizing agents was found to be not significantly higher than that of the serum. The results of ph-measurements indicate that the proximal tubule in Necturus does not participate in urinary acidification, and no evidence of preferential reabsorption of bicarbonate could be demonstrated. The results resolve some discrepancies of earlier micropuncture studies and are in good agreement with known data on osmotic pressure and sodium concentrations in proximal tubule fluid of Necturus.