An Investigation of the Actions of Aldosterone on Perfused Cat Kidneys, by Ureteric Stop-Flow Analysis

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Abstract
Stop-flow analysis, adapted for use on perfused cat kidneys, has been used for the study of the modifications induced in the reabsorption of salt, and water by blood from headless donor animals and by aldosterone. 1. the supranormal rates of excretion of salt and water found when cat kidneys are perfused with blood from headless or bypophysectornized donor animals result from impairment of proximal water-linked salt reabsorption. Distal sodium reabsorption proceeds normally (cf. figs. 2 and 3). 2. Aldosterone, in blood from headless animals, depresses further this impaired proximal reabsorption of salt and water arid so produces an overall diuretic and sodium-losing effect (fig. 4). 3. Aldosterone, in blood from intact animals, increases not only the distal rate of sodium reabsorption but also the proximal water-linked reabsorption of salt and water (fig. 4). This explains the antidiuretic effect of aldosterone on these preparations. 4. Oxytocin enhances the effects of aldosterone in blood from intact donor animals (cf. figs. 6 and 4). Oxytocin converts the diuretic action of aldosterone in blood from head-less animals (fig. 4) into an antidiuretic sodium retaining nne, by sensitizatioct of the proximal segments to the salt and water retaining action of aldosterone (cf. figs 5, 6 and 7).