Age-related changes in benzylamine oxidase activity in rat tissues.

Brain, liver, heart, lung, kidney and duodenum benzylamine oxidase (BZAO) activities were measured from young and old rats. Protein content was found to decrease in liver (-17%), kidney (-20%) and duodenum (-17%) but remained unchanged in brain, heart and lung of old rats compared with that of young rats. A significant decrease (-41%) of BZAO activity was found in lung whereas a significant increase of enzyme activity was found in brain (+49%) and kidney (+25%) and no change was found in heart and duodenum of old rats. BZAO was not detected in either young or old rat liver. Kinetic analysis for lung BZAO activity of old rats showed that Vmax was decreased but Km was unchanged in comparison with that of young rats. Since, as we have shown previously, MAO-A and -B activity in lung of old rats was also found to be decreased, the decrease of lung BZAO activity with increasing age merits further investigation, lung playing an important role in removing amines from the circulation.