The fate of the luminal asymmetric unit membrane of the superficial cell of the rat transitional epithelium

Abstract

The fate of the luminal asymmetric unit membrane (AUM) of the superficial cell of the transitional epithelium of the rat urinary bladder was electron microscopically and cytochemically investigated using exogenously administered horseradish peroxidase (HRP) as tracer. HRP-positive discoidal vesicles were formed by the folding of the AUM of the luminal surface plasma membrane. With the passage of time, these vesicles changed their shapes and were finally transformed into lysosomes by the following possible routes: 1) by becoming multivesicular bodies (MVBs); 2) by directly fusing with lysosomes; and 3) by becoming autophagic vacuoles. Another possibility would be reutilization.