The relationship between urinary inhibitory activity and endogenous concentrations of glycosaminoglycans and uric acid: comparison of urines from stone-formers and normal subjects.

The inhibitory effect of urine from 64 male stone-formers and from 42 normal men on the growth and aggregation of calcium oxalate crystals was measured. The degree of inhibition of each urine specimen was related to the endogenous concentrations of glycosaminoglycans, uric acid, and creatinine, and to the ratio of glycosaminoglycan to uric acid concentrations. No significant difference between the two groups of subjects with regard to the effect of urine on crystal growth or aggregation was found. Inhibitory activity was found to be significantly correlated with the urinary concentration of glycosaminoglycans, creatinine and uric acid, but not to the ratio of glycosaminoglycan/uric acid concentrations. It was concluded that urinary inhibitory activity depends only partly on the endogenous concentration of glycosaminoglycans and that the inhibitory activity of these compounds in vitro does not depend on the associated level of uric acid in the urine.