Direct inhibition of gastrointestinal carbonic anhydrase by ethanol

Carbonic anhydrase (CA) was found to be equally susceptible to direct inhibition by ethanol, whether the enzyme originated from homogenates of rabbit gastric, duodenal, or ileal mucosa. When gastric mucosa was separated into a soluble (cytoplasmic) and a membrane fraction, the membrane CA was more susceptible to ethanol inhibition, but less susceptible to acetazolamide inhibition, than the soluble enzyme. Male rat liver CA is relatively insensitive to acetazolamide inhibition, while female rat liver CA shows a sensitivity similar to that of other tissues. We found ethanol inhibited male and female rat liver CA equally, indicating a different site, or mode, of inhibition for ethanol and acetazolamide.