Identification of proteins extracted from calcium oxalate and calcium phosphate crystals induced in the urine of healthy and stone forming subjects (original) (raw)

1998, Urological Research

The purpose of our study was to identify the proteins and investigate the dierences, if any, between protein components of the matrices of calcium oxalate (CaOx) and calcium phosphate (CaP) crystals induced in vitro in whole human urine of healthy individuals and kidney stone patients. In addition, preliminary studies were performed to understand the eect of centrifugation and ®ltration of urine on its protein contents. Crystallization in urine was induced by addition of an oxalate or phosphate load. Crystals were collected, washed, and analyzed by scanning electron microscopy, X-ray diraction, and energy dispersive X-ray microanalysis. Matrix proteins were obtained by demineralization with ethylene diamine tetraacetic acid (EDTA), analyzed by polyacrylamide gel electrophoresis, and identi®ed by western blotting technique. No signi®cant dierences were detected between protein components of the matrices of CaOx and CaP crystals and between the crystal matrices obtained from the urine of normal and stone forming subjects. Albumin (AB), inter-a-inhibitor (IaI) related proteins, a-1 microglobulin (a-1 m), osteopontin (OPN), prothrombin (PT)-related proteins and Tamm-Horsfall protein (THP) were identi®ed in matrices of both CaOx and CaP crystals induced in urine from both the normal subjects and stone formers. AB, PT-related proteins and OPN were the main constituents. The other proteins were present in smaller but detectable amounts. However, CaP crystal matrix, contained a large amount of THP. In addition CaP crystals contained signi®cantly more proteins than CaOx crystals. Centrifugation and/or ®ltration of the urine resulted in reduction of many high molecular weight proteins including THP, AB and OPN in the urine.