The response of junctional complexes to induced desquamation in mouse bladder urothelium

During desquamation, the cells of mouse urinary bladder epithelium undergo detachment. Ln this process we examined the disconnection of cell adhesion molecules. Two proteins of cell junctions were studied: ZO1 of tight juncti ons and desmoplakin of desmosomes. Desquamation was induced by intravesical injection of LPS, constant illumination of mouse for 96 h, application of a combination of stress hormones hydrocortisone and norepinephrine or by re moval of calcium with EGTA. All the inducers caused penetration of lanthanu m tracer through the tight junctions, indicating paracellular permeability. Dilatation of extracellular spaces between neighboring cells was seen when ever desquamation was induced in bladders containing urine. Desquamation of single cells as well as groups of cells was observed. Contrary to obvious disconnection of cell junctions, as a precondition for desquamation, the di stribution of junctional proteins did not change either in urothelial tissu e or in desquamated cells. This study demonstrates that all the inducers of desquamation cause first an extensive dysfunction of a blood urine barrier and after that an occasional mechanical disconnection of adhesive junction s which consequently leads to desquamation. (C) 2000 Editions scientifiques et medicales Elsevier SAS.