Histochemical localization of carbonic anhydrase in the trachea of the guinea pig

Tissue specimens from guinea pigs were examined using an enzyme-histochemical reaction to explore the presence of carbonic anhydrase (CA) activity in the trachea. CA activity was detected in a group of morphologically distinct epithelial cells, in goblet cells, and in glands of the tracheal mucosa. The epithelial cells showing CA activity were distributed singly and sparsely throughout the entire trachea. These cells showed a wide morphological variability and were clearly different from those forming the pseudostratified ciliated epithelium. Their number was higher in sections closer to the tracheal bifurcation than in those near the larynx. Although the nature of these cells is unknown, based on their molphological and histochemical characteristics and their distribution, they may represent a specialized chemoreceptor. To our knowledge, this is the first report of CA localized in tracheal epithelial cells.