BIOASSAY OF DIURETICS

¹ From the Lederle Laboratories, Pearl River, N. Y.

1. A method using white rats has been devised for the bioassay of diuretics. It has been tested experimentally and statistically and applied to the study of various substances. Urea with an activity of 1 was taken as the standard diuretic.

2. The dose-action curves (log dose in millimols per kilogram body weight, plotted against log diuretic action) of urea, various salts, and salyrgan were found to be straight lines of similar slopes within a suitable range of doses. From these the diuretic activities of the substances were calculated. The doseaction curves of the xanthine derivatives were found to be complex, seemingly limited by a physiological factor.

3. Biuret, a urea derivative, assayed in this way, showed a diuretic activity of 1.4.

4. The following diuretic activities were determined from the dose-action curves: salyrgan, 400; bismuth potassium tartrate, 219; theophylline, 115; caffeine, 32; theobromine, 7.2; potassium nitrate, 3.9; sodium nitrate, 2.9; potassium acetate, 3.4; sodium acetate, 2.0; ammonium chloride, 2.7; and urea, 1.0.

5. Relatively large doses of the salts and urea removed much more water than that which was administered, whereas such doses of the xanthine diuretics, Bi tartrate and of salyrgan not only failed to produce an increase in diuretic action, but in most instances produced a decrease.

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