CALCIUM-OXALATE CRYSTALLIZING PROPERTIES OF POLYANIONS ELABORATED BY CULTURED VENAL PROXIMAL TUBULAR CELLS

To study the influence of renal polyanions on crystallization of urina ry calcium oxalate, we recovered polyanionic macromolecules from media conditioned by primary cultures of renal proximal tubular epithelial cells of rats in serum-free, hormonally defined medium. Cells cultured on microporous supports showed a higher degree of morphological and f unctional proximal differentiation into a polarized monolayer than tho se on plastic impervious substrata. Papainization of the polyanions yi elded the glycosaminoglycans chondroitin/dermatan sulphate and heparan sulphate. These accounted respectively for 60% and 80% of the crystal nucleation-promoting activities of polyanions recovered from the apic al and basal media conditioned by polarized cultures on microporous su pports. Similar relative activities were observed among the urinary gl ycosaminoglycans and polyanions similarly tested. Primary cultures of polarized proximal tubular epithelial cells are useful then as an in v itro model to study the crystallizing activities of polyanionic macrom olecules produced by renal cells.