Activity of class I, II, III, and IV alcohol dehydrogenase isoenzymes in human gastric mucosa

The gastric alcohol dehydrogenase (ADH) plays an important role in the "first pass" metabolism of ethanol. Human ADH exists in multiple forms, grouped into six classes and located in different tissues. In present study we investigated the activity of four classes (I, II, III, and IV) of alcohol dehydrogenase isoenzymes in the different parts of stomach (corpus and antrum) in patients with suspected gastric ulcer. The aim of the study was assess the particular role of different classes of ADH in the gastric dehydrogenase activity. For the measurement of the activity of class I and class II isoenzymes, we employed new fluorometric methods with specific substrates. The activity of class III alcohol dehydrogenase was measured by the photometric method with n-octanol and class IV with m-nitrobenzaldehyde as a substrate, respectively. All biopsy specimens were taken from less changed areas of the antrum and body of the stomach of 68 patients suspected of having gastric ulcer. It was found that ADH IV (gastric) activity was the highest (14.76 +/- 0.68 in the corpus of the stomach in men; and 7.61 +/- 0.68 in women, respectively). The activity of the ADH III isoenzyme was lower than that of ADH IV. The activities of class I and II ADH isoenzymes were barely detectable. All tested classes of ADH had higher activity in the corpus than in the antrum and in males than in females. In conclusion, the most important form of gastric ADH is isoenzyme of class IV, less important is the isoenzyme of class III. ADH classes I and II seem to have no role in the stomach.