A quantitative cytochemical method for measuring carbonic anhydrase activity.

Components of a histochemical method for demonstrating carbonic anhydrase activity have been investigated quantitatively. It was found that it is not necessary to use free-floating sections provided the reaction is done in a reaction medium of controlled depth. This permits the use of normal cryostat sections on glass slides, so making this technique applicable to the cytochemical bioassay of gastrin. The better control of the pH of the reaction, and changes in the concentration of phosphate and of cobalt, have resulted in a quantitatively reproducible reaction in the parietal cells of guinea-pig fundus. The reaction product is measured by microdensitometry. The specificity of the carbonic anhydrase reaction has been tested by the response elicited by gastrin acting on the parietal cells in vitro and by the use of acetazolamide.