STUDY OF THE IONIZED CALCIUM IN URINE

THE IONIZED CALCIUM IN ARTIFICIAL URINE AND THE EFFECT OF CITRATE ON THE PRECIPITATION OF CALCIUM PHOSPHATE

Abstract

The comparison between the measured value of ionized calcium (Ca⁺⁺) by means of the selective ion sensitive electrode and the calculated value by the computor was performed with particular interest in the effect of citrate on the precipitation of calcium phosphate.
The mean value of measured %Ca⁺⁺/total calcium was 42% in the artificial urine at pH 5.7 and 39% in the urine of five normal subjects at pH 6.0. The calculated value in artificial urine was 53% at pH 6.0. Among the components of artificial urine, citrate was the most effective to decrease Ca⁺⁺, which was followed by sulphate and phosphate. As an exception magnesium increased Ca⁺⁺. The precipitation in the calcium and phosphate containing solution could be detected by the sudden decrease of Ca⁺⁺, which could be observed by only the measured value. The calculated value showed no information concerning the precipitation. The Ca⁺⁺ decreasing effect of citrate became predominant according to the increasse of pH and reached almost the maximum at pH 8. The precipitation point, pH at which the precipitation occurred, moved apparently to a more alkali side by the application of citrate.
The possible application of citrate to urolithiasis was discussed on the basis of the present findings.