Carbon monoxide insensitivity of gastric acid secretion.

By the use of hyperbaric conditions, it is possible to obtain high CO/O2 while maintaining O2 tension at a level that is not in itself inhibitory of acid secretion in the isolated frog gastric mucosa. Free solution CO/O2 of up to 10:1 only inhibit acid secretion about 20%, less than expected. Considerations of O2 diffusion into a respiring tissue bounded by unstirred layers predict a CO/O2 at the terminal oxidase ranging from 12 to 64 under various conditions and positions in the tissue, with predicted inhibitions between 55 and 86%. The inhibition observed is light reversible, affects potential difference and resistance in a consistent manner but is never very large. In the absence of O2, the CO-cytochrome alpha 3 complex can be demonstrated spectrophotometrically. Among other possible explanations for these observations, it is suggested that this tissue may contain an inhibitor-insensitive oxidase for a portion of the cytochrome system directly involved in acid secretion.