CARBONIC-ANHYDRASE IS PRESENT IN HUMAN ESOPHAGEAL EPITHELIUM AND SUBMUCOSAL GLANDS

Carbonic anhydrase (EC 4.2.1.1) activity was investigated in normal hu man oesophageal mucosa using the Hansson and Ridderstrale catalytic co balt methods. The enzyme was detected in the cell membranes and nuclei and, to a lesser extent, in the cytoplasm of the epithelial cells of the mucosa giving a 'chicken wire' appearance. Activity decreased towa rds the lumen. Other stratified squamous epithelia - buccal mucosa, ec tocervix and skin -gave a similar pattern. Acinar cells of oesophageal submucosal glands also exhibited activity for the enzyme, but the duc ts did not. The formation of reaction product was prevented by acetazo lamide and ethoxzolamide and by the omission of bicarbonate from the s ubstrate medium. Carbonic anhydrase in oesophageal squamous epithelium may be involved in the control of intra- and extracellular pH, while that in the glands is more likely to be concerned with bicarbonate sec retion.