Background: Human gastric mucosa contains three alcohol dehydrogenase (ADH) isozymes (classes I, III, and IV). Various factors such as Helicobacter pylori infection, sex, age, and the part of the stomach involved have been suggested to affect alcohol dehydrogenase activities, although these views are controversial. In this study, these unsettled issues were reexamined. Methods: Activities of class I and IV ADHs were evaluated in the cytosolic fraction of human gastric mucosa samples by reduction of their preferred substrates, namely acetaldehyde and m-nitrobenzaldehyde, and activities of class III were evaluated by oxidation of its preferred substrate, formaldehyde. Then, effects of Helicobacter pylori infection, sex, age, and the part of the stomach involved were examined. Results: Class I, III, and IV ADH activities were 17.5 ± 8.4, 4.2 ± 2.5, and 8.9 ± 3.9 nmol of nicotinamide adenine dinucleotide oxidation per minute per milligram of protein, respectively, for the entire population. Helicobacter pylori infection significantly reduced class I and IV ADH activities but did not affect activity of class III. In the samples without Helicobacter pylori infection and severe gastritis, sex did not affect class I, III, or IV ADH activities. In the same series, class IV ADH activity significantly decreased with age (p = 0.006), whereas no correlation was found between age and ADH activity of class I and III ADHs. The level of class IV ADH activity was significantly higher in the upper body than in the lower regions, whereas no such heterogeneity was observed in class I and III ADH. Conclusions: Various factors affect human gastric ADH activities, such that careful interpretation of their significance is necessary.
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