Succinic and Malic Oxidase in Gastric Hydrochloric Acid Production

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Abstract
Effect of histamine on the activity of succinic oxidase and malic dehydrogenase was studied in guinea pig and human gastric mucosa. Human tissue was obtained through the surgical services of the Boston City Hospital. Control value for the succinic oxidase system of the proximal half of the guinea pig stomach was approximately 480 (Qo2 (N) (µl O2/mg nitrogen/hr.)). After histamine, this value rose to 550 in 30 minutes with a simultaneous rise in titratable acidity of the stomach contents. Animals fasted for 72 hours had a Qo2 (N) of approximately 500 and after histamine a Qo2 (N) of 700 was observed. Spectrophotometric analysis of succinic dehydrogenase and cytochrome oxidase activities, two of the major components of the succinic oxidase system, revealed that both components are increased following histamine administration. Malic dehydrogenase, however, was not affected by histamine treatment. Succinic dehydrogenase was demonstrated by histochemical localization and was concentrated below the superficial mucous layer where parietal cells were abundant. Succinic oxidase activity of human gastric mucosa was demonstrable only in those specimens containing abundant parietal cells. This study confirms the view that HCl production by parietal cells is associated with aerobic metabolism and is perhaps under enzymatic control. The study suggests that the succinic oxidase system may be involved in the production or secretion of HCl.

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