The effects of human urine on the adhesion of calcium oxalate crystal to renal tubular cells

Abstract

We examined the effects of human urine on the adhesion of calcium oxalate monohydrate (COM) crystals to Madin-Darby canine kidney (MDCK) cells in vitro. Quantitative assay of COM crystal adhesion to MDCK cells: MDCK cells were exposed to COM crystal suspension for 5 minutes. Various urine samples were added in the COM crystal suspension. The adherent COM crystals on the MDCK cells were dissolved by 5 N hydrochloric acid. Calcium concentration of the solution was measured by atomic absorption analysis to quantify the volume of adherent COM crystals. This assay was applied for the experiments as follows. (1) Effect of human urine on COM crystal adhesion. (2) To investigate whether human urine inhibited COM crystal adhesion by acting on the crystal surface or on the cell surface. (3) Isolation of the substance from human urine that inhibits COM crystal adhesion. (4) Comparison of the inhibitory activities of the urine between from stone formers and healthy controls. (1) Human urine had a strong inhibitory effect on COM crystal adhesion to MDCK cells. (2) The capacity of human urine to inhibit adhesion of COM crystals to MDCK cells was shown to be mediated by their ability to act on the crystal surface. (3) We isolated a macromolecular fraction (MW 60,000) that had strong capacity to inhibit cellular adhesion of COM crystals through ion exchange and gel filtration chromatography. (4) Nine urine samples from stone formers demonstrated extreme low inhibitory activities, which supposed us that the inhibitory capacity of the urine against crystal adhesion might be one of the risk factors in kidney stone formation.