Immunohistochemical Study on the Distribution of Carbonic Anhydrase Isozymes in Rat Small Intestine

Chun, Byeong Jo; Na, Jin Hee; Nam, Kwang Il; Lee, Seung Won; Ahn, Kyu Youn; Bae, Choon Sang; Park, Sung Sik

Abstract

Carbonic anhydrase catalizes the reversible hydration of carbonic dioxide and participate in various biological processes. There are several isozymes and differ in their kinetic properties, tissue distribution and subcellular localization. The expression of carbonic anhydrase isozymes in digestive tract vary according to animal species and region of the tract. The distribution of carbonic anhydrase (CA) isozymes I, II, IV and IX was investigated in various portions of the rat small intestine using Western blotting analysis and immunohistochemical staining. Western blotting analysis of rat small intestine revealed that CAI was found to be abundantly expressed throughout the small intestine. Expression of CAII in duodenum was much higher than that in jejunum and ileum. Expression of CAIV and IX was found to be weak throughout the small intestine. Immunohistochemical reaction revealed no staining of CAI in all parts of small intestine except blood vessels. CAII was detected at the supranuclear cytoplasm of surface epithelium, but not in intestinal gland. Staining intensity was most strong in the proximal duodenum. CAIV was detected at the apical surface of epithelial cells of villi, and showed most strong staining intensity in the terminal ileum. CAIX was detected at the surfcae epithelium, cells of intestinal gland and Brunner's gland, and the positive reaction was confined to the supranuclear cytoplasm. CAIX differed from CAII in tissue distribution, but subcellular localization of CAIX and II were the same. These results indicate that the surface epithelium of small intestine express CAII, IV and IX, intestinal gland and Brunner's gland express CAIX, and suggest that CAIX may somewhat contribute the control of acid-base balance in the small intestine.