Comparison of fibronectin content in urinary macromolecules between normalsubjects and recurrent stone formers

Objectives: Fibronectin (FN: 230 kD) is a multifunctional alpha (2)-glycopr otein distributed throughout the extracellular matrix and body fluids. Rece nt studies have shown that a variety of molecules, including FN, inhibit th e endocytosis of calcium oxalate (CaOx) crystals in vitro. We recently repo rted that FN was oversecreted from the renal tubular cells as a result of t he stimulation of CaOx crystals, and inhibited the aggregation of CaOx crys tals and the adhesion of CaOx crystals to the renal tubular cells. In the p resent study, we investigated the difference of FN content in urinary macro molecules (UMMs) between normal subjects and recurrent stone formers. Materials and Methods: Urinary parameters in relation to urolithiasis of no rmal subjects and recurrent stone formers were measured. Proteins in extrac ted UMMs from urine of normal subjects and recurrent stone formers were mea sured with a BioRad protein assay, GAGs in each UMMs with a modified DMB as say and the FN content with the ELISA method. Results: In urinary parameters, citrate was significantly higher in urine f rom normal subjects (female) than normal subjects (male) or recurrent stone formers, and the other parameters showed no differences between each group . The protein concentrations in UMMs showed no differences between each gro up. Normal subjects (male and female) showed a significantly higher concent ration of GAGs than recurrent stone formers (with and without silent stone) . Compared with normal subjects and recurrent stone formers without silent stones, higher FN levels were found in recurrent stone formers with silent stones. Normal subjects showed a significantly higher concentration of FN t han recurrent stone formers without silent stones. No difference in FN leve l was shown between normal subjects (male) and normal subjects (female). Conclusion: Recurrent stone formers with silent stones showed a significant ly higher concentration of FN in UMMs than normal subjects. This finding su ggests that FN might be oversecreted from the renal tubular cells as a resu lt of the stimulation of CaOx stones in vivo. Recurrent stone formers witho ut silent stones showed a significantly lower concentration of FN in UMMs t han normal subjects. From this finding it is suggested that FN might play a role as a potent inhibitor of CaOx urolithiasis in a clinical setting. Cop yright (C) 2001 S. Karger AG, Basel.