PERMEABILITY OF RAT TRANSITIONAL EPITHELIUM - RELATIONSHIP BETWEEN STRUCTURE AND FUNCTION

SUMMARY.— Both the transitional epithelium of the mammalian urinary bladder and the epidermis of skin are specialized to prevent loss of endogenous water. Under abnormal circumstances, the bladder epithelium may differentiate into a stratified, cornified epithelium which closely resembles normal epidermis. It thus has the capacity to produce some of the same subcellular components, including proteins, as skin and may indeed do so normally. The water barrier in the bladder, like that in skin, depends on the integrity of a thick proline‐rich cell membrane, but whereas this membrane is water permeable in the skin, the evidence suggests it to be impermeable to water in the bladder. Some of the similarities and differences between the barriers to loss of endogenous water in skin and bladder, and their possible mechanisms of action are discussed. Copyright © 1969, Wiley Blackwell. All rights reserved