Potassium Bicarbonate Supplementation Blocks the Hypocalciuric Response to Hydrochlorothiazide in Rats

Goulding, A.
Mcintosh, J.

From the Department of Medicine, University of Otago, Dunedin, New Zealand

^*Requests for reprints: Dept. of Medicine, University of Otago Medical School, P.O. Box 913, Dunedin, New Zealand.

Accepted January 24, 1985.

Supported by the Medical Research Council of New Zealand and by the Sir John Roberts Bequest Fund.

Journal of Urology 133(5):p 891-893, May 1985. | DOI: 10.1016/S0022-5347(17)49274-3

ABSTRACT

Bicarbonate salts and thiazide diuretics each lower urinary calcium excretion. This study was undertaken to compare the effects of administering oral sodium or potassium bicarbonate supplements (4.5 mmol./day of each salt) each with or without hydrochlorothiazide (10 mg./kg. body weight/day) on urinary calcium excretion in rats. Urinary calcium decreased (p <0.01) by about 50 per cent after sodium bicarbonate supplementation and potassium bicarbonate supplementation. The hypocalciuric response to each bicarbonate salt was similar. However, although hydrochlorothiazide depressed urinary calcium in rats consuming sodium bicarbonate, rats receiving equimolar supplements of potassium bicarbonate did not lower urinary calcium when given hydrochlorothiazide, despite evidence of the expected thiazide-mediated diuresis. It is concluded that in the rat potassium bicarbonate loading blocks the ability excretion.