URINARY MACROMOLECULES ARE PROMOTERS OF CALCIUM-OXALATE NUCLEATION INHUMAN URINE - TURBIDIMETRIC STUDIES

Calcium oxalate crystallization was induced in the filtered, ultrafilt ered (10 kDa) and retentate fractions of 24-h urine specimens obtained from 15 male controls and 10 male stone formers, by administration of an aqueous sodium oxalate challenge to each test solution. Crystalliz ation rates were followed by monitoring of the increase in turbidity i n these fractions as a function-of time. A laboratory nephelometer, pr eviously calibrated against a Coulter counter, was used for this purpo se. In addition, to facilitate interpretation of turbidity data, a Mal vern particle size analyzer was used to determine crystal sizes and nu mbers in control urines. Crystallization rates, crystal numbers and cr ystal sizes were generally lower in ultrafiltered Fractions than in fi ltered or retentate fractions, indicating that urinary macromolecules are promoters of calcium oxalate nucleation. Data for stone formers su ggest that the urinary macromolecules in this group may be more potent nucleation promoters than those in controls.