Experimental Urolithiasis: X. On the State of Calcium in the Urine

Abstract

To investigate the state of Ca in the urine, the presence of complexed or bound Ca was tested by means of an ion exchange resin technique, and a comparison was made of the speed with which Ca will dialyze from urine and pure solutions. The experiments suggest that part of the Ca in urine is not in the positively-charged cationic form but is bound to some other substance. Presumably much of the bound portion is present as an ionic complex with citrate. The dialysis experiments show that a considerable portion of the urinary calcium is loosely bound to some other substance not easily dialyzable. Calcium binding presumably plays a role in increasing the solubility of the Ca salts in urine. No difference was found in the proportion of bound or complexed Ca when normal urine was compared with urine from stone-formers.