HISTOLOGY, HISTOCHEMISTRY AND ELECTRON MICROSCOPY OF THE TRANSITIONAL EPITHELIUM OF THE RAT URINARY BLADDER IN RESPONSE TO INDUCED PHYSIOLOGICAL CHANGES

Abstract

The histological, histochemical and fine structural appearances of transitional epithelium were studied in the empty rat bladder and after filling with solutions of varying chemical composition, concentration and pH. The epithelium, which rests upon a distinct basement membrane, is composed of three cell layers. Cells of the surface layer are characterised by the presence of numerous vesicles, the majority of which are compressed, fine fibrils, and some dense granules. Cells of the intermediate layer possess fewer vesicles and less fibrillar material than the surface cells and basal cells are devoid of specialised cytoplasmic structures. Filling the bladder with distilled water resulted in an increased activity of alkaline phos-phatase and an increase in the number of dense granules and of vesicles. Filling the bladder with physiological saline, 5% sodium chloride, 10% glucose and 8% sodium bicarbonate solution produced no histochemical changes and no signficant changes in fine structure. The findings indicate that the transitional epithelium of the rat bladder is sensitive to a hypotonic environment whereas it appears well adapted to. a hypertonic or isotonic environment. The possible significance of the various specialised cytoplasmic structures is discussed in relation to the experimental findings.