Hydration feature of urinary compounds. Evidence for molecular abnormality in calcium oxalate urolithiasis

Proton-relaxation-time measurements were performed on lyophilized urine samples collected from 11 recurrent calcium oxalate stone-formers, 9 uric acid stone-formers, 9 patients with various urological disorders, and 20 normal individuals. The T1 and T2 relaxation times were determined using a Bruker PC Multispec at 20 MHz at 37 degrees C for measurements of lyophilized sample and thereafter during gradual controlled rehydration. The prolongation of the relaxation times as a function of rehydration was found to differ significantly (P less than 0.005) between, on the one hand, the calcium oxalate stone-formers and, on the other hand the normal, uric-acid stone-formers, and patients with other urological disorders. Water compartmentalization was then calculated according to the fast proton diffusion model. At most of the experimental points during rehydration process, significantly (P less than 0.001) less water was bound to the compounds of urine from calcium oxalate stone-formers than that obtained from normal individuals. The variations in the bound hydration water may have been associated with possible changes in the structure or configuration of the compounds present in the urine of the different groups. The results reflect differences in the urinary content and/or properties of normal subjects and calcium oxalate stone-formers, and indicate that the mechanism of bound water relaxation is in some way specific to the pathophysiological state of urine.