Identification and intracellular localization of carbonic anhydrase I in gills, heart, muscle, and intestine of rainbow trout, Oncorhynchus mykiss

Carbonic anhydrases (CAs) play a key role in physiological functions such as pH homeostasis, calcification, photosynthesis, and ionic regulations. Among CA isozymes, CA I is a specific marker for the cytoplasm or apical cell membranes of colonic epithelial cells, and it is related to enterocyte proliferation in mammals. The major aim of the present study was to investigate the regional, cellular, and subcellular localization of CA I in a fish, rainbow trout, Oncorhynchus mykiss. The CA I was identified in the gills, heart, and intestine of the rainbow trout. CA I protein detected in the tissues of the rainbow trout was similar to a CA III with a molecular weight of 29 kDa. Immunohistochemical results demonstrated that CA I was localized in the various cells of gills, heart, muscle, and intestine of the rainbow trout.