STOP-FLOW ANALYSIS OF RENAL TUBULAR FUNCTION IN THE RAT UNDERGOING OSMOTIC DIURESIS DUE TO CREATININE LOADING.

Abstract

Summary1. A brisk osmotic diuresis was produced in rats by the intravenous infusion of 8 per cent creatinine in Ringer's solution at 0·39 ml./minute. Steady‐state conditions were attained after 25 minutes of infusion. During the period of infusion between 25–43 minutes, six urine and three plasma samples were collected in each of a series of seven animals, and the creatinine clearance and urinary excretion of water, creatinine, sodium and potassium were found to be constant. Mean values and standard deviations between animals were: 0·58 ± 0·09 ml./minute (water); 17·7 ± 2·4 mg./minute (creatinine); 59·6 ± 16·7 μEq./minute (sodium); 12·9 ± 3·1 μEq./minute (potassium); 2·69 ± 0·68 ml./minute (creatinine clearance). Standard deviations within animals were: 0·05 ml./minute (water); 0·83 mg./minute (creatinine); 9·08 μEq./min. (sodium); 0·91 μEq. /minute (potassium); 0·16 ml./minute (ereatinine clearance). Sodium and potassium excretion both showed highly significant positive correlations with urine flow during creatinine and mannitol diuresis, but, at comparable urine flow rates, creatinine produced significantly greater rates of excretion of sodium than did mannitol.2. The stop‐flow technique for the localization of renal tubular function was found to be practicable in rats undergoing creatinine diuresis. During stop‐flow the intraureteric pressure rose within two minutes to a plateau between 41 and 50 mm. Hg. The stop‐flow patterns obtained for creatinine, para‐aminohippurate, sodium and potassium, resembled those reported previously in other animals.3. By means of the stop‐flow technique, the proximal tubule of the rat nephron was shown to secrete the organic acids phenolsulphonphthalein, trifluoromethyldisulphamylaniline, and para‐aminohippurate. In the same region of the nephron the amino acids phenylalanine, valine, alanine, glutamic acid.