Distribution of 4-nitroquinoline 1-oxide reductase in the mucosa of canine digestive tract.

The distribution of 4-nitroquinoline 1-oxide (4-NQO) reductase, assumed to be closely related to the carcinogenesis of 4-NQO, was investigated in the mucosa of canine digestive tract, and its results indicated following points. 1) The activity of 4-NQO reductase was highest in the esophagus, next in the stomach, and remarkably low in the small and large intestines. 2) There is no significant difference in the 4-NQO reductase activity between the upper, middle, and lower portion of the esophagus, but its activity was higher in the female than in the male in its upper and middle portions. 3) Among the esophageal tissue, its activity was high only in the mucous epithelium and very low in all other layers. 4) Most of the enzymic activity in the esophageal mucosa existed in the cytosol fraction and activity of the microsome fraction was remarkably low. Even if NADPH or NADH was used as the hydrogen donor, its activity was not different in the cytosol fraction, but the former was a better hydrogen donor in the microsome fraction. 5) In the gastric mucosa, the enzymic activity was equally high in various portions of the corpus ventriculi; the greater and lesser curvatures, anterior and posterior parietes, and fundus. It was remarkably low only in the pyloric antrum.