Immunohistochemical localization of carbonic anhydrase isozymes I, II and III in the bovine salivary glands and stomach.

The immunolocalization of carbonic anhydrase (CA) isozymes in bovine salivary glands and stomach were first investigated in order to discuss their biologic functions. In parotid glands, CA-II was located in serous acinar cells, whereas CA-III, in the duct segments. In contrast, a strong reaction was shown for both CA-II and CA-III in the duct segments of the submandibular gland, especially CA-III was selectively located in basal cells of the interlobular ductal epithelium; however, these glands essentially lacked CA-I. On the other hand, epithelial cells of the rumen, reticulum and omasum showed cytoplasmic reaction for CA-I, II and III in all layers of the epithelium, except the stratum coroneum. The parietal cells in the abomasal epithelium were more intensely stained for CA-II, but not for CA-I and CA-III. Immunolocalization of CA isozymes in serous cells in the parotid gland indicates their primary function in secreting macromolecules, whereas localization of CA in striated and excretory ducts in the parotid and submandibular gland suggests their traditional function in fluid and electrolytic transport. The biologic function of CA isozymes in the ruminal, reticular and omasal mucosa are postulated to influence the absorption and excretion of volatile fatty acid and NH4; the abomasal parietal cell is considered to be involved in ion transport.