Effect of different fractions of macromolecules upon triggering of calcium oxalate and calcium phosphate crystal formation in whole urine.

Macromolecules were removed from whole urine samples by sequential ultrafiltration using molecular weight cut-offs of 300,000, 100,000 and 10,000 dalton. The whole urine samples and ultrafiltrates were evaporated to 1,250 mosm/kg at pH 5.3 and 6.8 to study calcium oxalate and calcium phosphate crystal formation, respectively. While all the ultrafiltrates removed Tamm-Horsfall proteins and most of the crystal formation, there was some 10% of the crystal-promoting powers in the macromolecules in the fraction between molecular weight 100,000 and 300,000 dalton. This demonstrates the existence of a second crystal-promoting substance in the macromolecules of whole urine.