Succession of events in desquamation of superficial urothelial cells as a response to stress induced by prolonged constant illumination

The effect of moderate stress induced by prolonged illumination was analyse d on urothelial cells of female mouse urinary bladders at ultrastructural a nd cytochemical levels. This study demonstrates that the urothelium respond s to moderate stress with desquamation which involves two subsequent steps. The first step includes a local detachment of tight junctions and conseque ntly the loss of the permeability barrier leading to expanded intercellular spaces among urothelial cells. During the second step, the disjunction of desmosomes accompanied by exocytosis of lysosomal enzymes (NADPase) in the intercellular space results in exfoliation of superficial cells. It is evid ent that moderate stress elicits an enhanced desquamation of only superfici al cells by a subsequent dysfunction of first tight junctions and after tha t adherens-type junctions. A rapid restoration of the new tight junctions p revents a long-term malfunction of the blood-urine barrier. (C) 2001 Harcou rt Publishers Ltd.