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

Objective. To determine the effect of human urine on the adhesion of calciu m oxalate monohydrate (COM) crystals to Madin-Darby canine kidney (MDCK) ce lls in a model system in vitro. Materials and methods. MDCK cells were exposed to COM crystals in the prese nce of various human urine samples. COM crystals adhering on MDCK cells wer e quantified by measuring the calcium concentration using atomic absorption analysis. The inhibitory activities were estimated individually for variou s urine samples from healthy subjects and recurrent stone formers. Results. 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 ur ine. Pretreatment of crystals with human urine before exposure to the cells significantly reduced crystal adhesion, suggesting that human urine altere d the properties of the crystal surface but not the cell surface. Conclusion. Coating of the crystals by some component(s) of human urine mig ht 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 ase unknown, a low potential for inhibiting: adhesion may be a risk factor in stone formation because it permits crystal adhesio n and retention in the tubules.