ADHESION, INTERNALIZATION AND METABOLISM OF CALCIUM-OXALATE MONOHYDRATE CRYSTALS BY RENAL EPITHELIAL-CELLS

The interaction between crystals that nucleate in the nephron lumen an d tubular cells could be an important determinant of renal calcificati on. Kidney epithelial cells in monolayer culture (BSC-1 line), used to model the tubule, rapidly bound and internalized crystals of calcium oxalate monohydrate (COM), the most common constituent of renal stones . Transmission and scanning electron microscopy, enzyme histochemistry , and kinetic analysis of [C-14]- labelled crystals were used to study the interaction between renal cells and COM crystals. Electron micros copy revealed that adherent crystals on the apical cell surface can se rve as sites for aggregation of additional crystals. Enhanced binding of exogenous crystals to plasma membrane domains overlying internalize d crystals was observed for at least 24 hours after the initial cell-c rystal interaction. Following internalization, crystals appeared to di ssolve within lysosomal inclusion bodies during the ensuing five to se ven weeks. Over this time, many cells still containing crystals cluste red together in the monolayer. These observations suggest that adhesio n and internalization can promote crystal retention in the nephron, wh ereas intracellular dissolution of crystals may serve as an important, hitherto unrecognized defense against pathologic renal calcification.