Stop‐flow Analysis of Renal Tubular Function in the Rat Undergoing Osmotic Diuresis Due to Creatinine Loading

Abstract

Summary 1. 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.

Is Magnesium Secreted by the Rat Renal Tubule?

“…The curves for sodium, PAH, and creatinine are similar to those reported previously in rats [17][18][19]. Magnesium exhibits a distal dip in the same region as sodium.…”

The effect of androgenic hormones on creatinine secretion in the rat

“…Failure of previous workers to demonstrate creatinine secretion on stop flow in the rat could be due to differences in technique. Young & Edwards (1964) used creatinine as the diuretic agent and so their rats had extremely high plasma levels of creatinine. It is likely that this fact served to mask any secretion which may have occurred.…”

“…ALICE M. HARVEY AND RICHARD L. MALVIN flow has been used extensively in the dog but far less frequently in the rat (Williamson, Skulan & Shideman, 1961;Young & Edwards, 1964). We have shown that the clearance ratio of creatinine to inulin in the male rat exceeds unity, indicating creatinine secretion in this animal (Harvey & Malvin, 1965).…”

“…We have shown that the clearance ratio of creatinine to inulin in the male rat exceeds unity, indicating creatinine secretion in this animal (Harvey & Malvin, 1965). Young & Edwards (1964) were not able to demonstrate creatinine secretion with the stop flow procedure in the rat, although it had been shown in the dog (O'Connell, Romeo & Mudge, 1962;Swanson & Hakim, 1962). This report deals with our attempt to confirm secretion of creatinine with the stop flow technique in the rat.…”

“…Young & Edwards (1964) used creatinine as the diuretic agent and so their rats had extremely high plasma levels of creatinine. It is likely that this fact served to mask any secretion which may have occurred.…”