The effects of human urine on the adhesion of calcium oxalate crystal to Madin-Darby canine kidney cells.

Abstract

To determine the effect of human urine on the adhesion of calcium oxalate monohydrate (COM) crystals to Madin-Darby canine kidney (MDCK) cells in a model system in vitro. MDCK cells were exposed to COM crystals in the presence of various human urine samples. COM crystals adhering on MDCK cells were quantified by measuring the calcium concentration using atomic absorption analysis. The inhibitory activities were estimated individually for various urine samples from healthy subjects and recurrent stone formers. Human urine inhibited the adhesion of COM crystals to MDCK cells, with some variations between individual samples. The most potent inhibition of crystal adhesion was expressed by the macromolecular fraction of the urine. Pretreatment of crystals with human urine before exposure to the cells significantly reduced crystal adhesion, suggesting that human urine altered the properties of the crystal surface but not the cell surface. Coating of the crystals by some component(s) of human urine might be an important physiological event in preventing adhesion or retention of crystals in the renal tubules. Although the mechanisms by which crystal adhesion is prevented are unknown, a low potential for inhibiting adhesion may be a risk factor in stone formation because it permits crystal adhesion and retention in the tubules.