Histochemical localization of cytochrome oxidase in gastric mucosa

A cytochemical technique for localizing cytochrome oxidase activity, based upon the oxidative polymerization of 3,3-diaminobenzidine (DAB) to an osmiophilic reaction product, has been employed to test the possibility of extramitochondrial cytochrome oxidase in gastric mucosa. Deposition of reaction product was found to be exclusively localized within mitochondris; in particular, no reaction product was observed at the apical plasma membrane. Measurements of the effect of DAB on acid secretion revealed a biphasic action consisting of an initial stimulation followed by inhibition. The stimulation of secretion of DAB is interpreted to indicate that DAB is oxidized via a pathway which is linked to the secretory process. The combined cytochemical and physiological measurements provide evidence that the metabolic energy supply for acid secreation is derived from mitochondrial reactions. The results are discussed in relation to current models for the coupling between acid secreation and oxidative metabolism.