The adult human female urethra. Enzyme-histochemical study.

In the female urethra, the activity and distribution of 15 enzymes was determined by using both conventional and special histochemical methods. The enzymatic equipment differed according to the type of epithelial lining whose variation is characteristic for the female urethra. In the stratified squamous epithelium of the urethra, alkaline phosphatase, beta-glucuronidase, acetyl-beta-D-glucosaminidase, thiamine pyrophosphatase, and glucose-6-phosphatase exhibited but minimal or no activity, yet the other 10 enzymes studied displayed activity particularly in basally situated cells. Nearer to the lumen of the urethra, the activity in the epithelium kept decreasing and was mostly absent in superficial and desquamated cells. In the pseudostratified columnar and in the transitional epithelium of the urethra, the majority of enzymes showed an evenly distributed activity at all epithelial levels. In the apical parts of the most superficially situated cells bounding the lumen of the urethra, a distinct narrow zone of higher activity was observed. It was seen not only on determining the majority of dehydrogenases but also on examining acid phosphatase and naphthyl esterase. The endocrine cells occurring in the uroepithelial lining of the female urethra displayed, yet always with the exception of squamous epithelium (Zaviacic et al. 1983), distinct activity of acid hydrolytic enzymes, and of the enzymes studied it was particularly acid phosphatase. The majority of the demonstrated enzymes, of the dehydrogenases priority, is to be given to succinate dehydrogenase, enabled to differentiate readily between the highly active striated muscle fibers located in the most peripheral parts of the excisions along the urethral circumference and the smooth musculature of the urethral wall with a lower or only minimal activity.