Partial biochemical and physicochemical characterization of organic macromolecules in urine from patients with renal stones and control subjects.

From the urine of patients with calcium nephrolithiasis, and of control subjects, we isolated organic substances according to molecular size and tested them for effects on calcium oxalate precipitation. Nine subgroup materials of varying sizes were prepared by ultrafiltration and Sephadex G-200 column chromatography from 10 stone-formers, as well as from 10 control subjects. Uromucoid was found in large materials of both groups, whereas glycosaminoglycans were detected in large- and medium-sized materials of both groups. The small materials were devoid of uromucoid and glycosaminoglycans, but contained protein and uronic acid, a finding suggesting that they may be glycoproteins. The daily excretion of the uromucoid-rich material was greater, but that of the small glycoproteins was lower in stone-formers than in control subjects. The largest-sized material from stone-formers was devoid of any activity on calcium oxalate precipitation. All of the remaining materials (at a concentration of 5 mg/dl) exerted inhibition on calcium oxalate precipitation. The inhibition rose progressively with the decreasing size of organic materials. The calculated total inhibitor activity for the stone-forming group was 36% lower than that obtained in the control group.