Role of biomolecules from human renal stone matrix on COM crystal growth

Human renal calculi surgically removed from kidney stone patients were obta ined and chemically analysed. Stones with CaOx (calcium oxalate) as the maj or component were washed in 0.15 M NaCl with gentle stirring for 48 h and t hen pulverised to a fine powder. The powder was extracted with 0.05 M EGTA, 1 mM PMSF and 1% beta- mercaptoethanol for 4 days at 4 degrees C, the susp ensions and the supernatants obtained were filtered through an Amicon Model 200 apparatus (mol. wt. cut off of 10,000 daltons) under nitrogen at 40 p. s.i. and concentrated to a known volume. The method of Nakagawa et al. [7] was employed to study the ability of > 10 kDa fractions to influence COM gr owth using metastable solution of CaCl2 and Na2C2O4 containing traces of C- 14-oxalic acid. Potent biomolecules having the ability to influence CaOx pr ecipitation were subjected to isolation, purification and characterization. Standard biochemical procedures, e.g. ultracentrifugation, ion-exchange ch romatography, molecular sieve chromatography and SDS-PAGE, etc., were emplo yed. Results revealed that human renal calculi extract contains biomolecule s that can inhibit as well as stimulate the growth of preformed COM (calciu m oxalate monohydrate) crystals. Most potent stimulator of CaOx growth was found to have a molecular weight of 66 kDa.