Carbonic anhydrase II is secreted from bovine parotid glands

Abstract

Besides carbonic anhydrase VI (CA-VI),CA-II is suggested to be a second secreted isoenzyme inruminant saliva. Therefore, the aim of the present studywas to investigate the expression of salivary CA-II inbovine parotid glands at the protein level. Moreover, weintended to identify the cells which secrete the enzymeinto the saliva. Two commercially available CA-IIspecific antibodies were tested for use inimmunohistochemistry on frozen sections of bovineparotid tissue. Intense positive staining for CA-II wasfound in luminal duct cells and for the first time alsoinside the duct lumen, clearly demonstrating theexpression and secretion of salivary CA-II in bovineparotid glands. The presence of CA-II protein wasverified for parotid tissue and whole saliva usingimmunoblot analysis. Both salivary CA-II and CA-VIare highly active in supplying the alimentary tract withbicarbonate. It is suggested that a decrease in theexpression of either one of these enzymes might severelydisturb digestion and/or increase susceptibility toacidosis in ruminants.