Proteins in renal stones and urine of stone formers

Knowledge of the essential characteristics of macromolecules constituting t he organic matrix of the nidus of urinary stones is required to understand the mechanism of urolithogenesis. The aim of this study was to isolate and characterise those stone nidus proteins. Using an extraction buffer contain ing SDS and p-mercaptoethanol, we were able to overcome known problems of p rotein isolation from urinary stone matrix. These proteins were characteris ed by a strong tendency to aggregate under reducing and denaturing conditio ns. On SDS-PAGE, their molecular weights range from less than or equal to 1 2 to 66 kDa. Antisera raised against stone matrix proteins showed a cross-r eactivity between proteins isolated from different stones irrespective of t heir origin or mineral composition. Moreover, urinary proteins from stone f ormers also cross-reacted with these whereas there was no reaction with uri nary proteins of non-stone formers. Western blotting confirmed these findin gs. Given the above summarised properties, it can be safely concluded that these proteins are prevalent in urines of stone formers, that they are sele ctively incorporated into renal stones of all aetiologies, and that they mo st likely have a role in nidus and, therefore, early stone formation.