Observations on the monamine oxidase activity of rat vasa deferentia, major blood vessels and human saphenous vein.

Monoamine oxidase (MAO) activity was characterized using whole tissue homogenates and kynuramine as the substrate. In rat vasa deferentia, kynuramine deamination was differentially inhibited by clorgyline, less so by deprenyl and not at all by pargyline. These studies, and mixed substrate experiments with tryptamine, proved that kynuramine is a substrate for MAO types A and B. Experiments made with rat abdominal aorta and inferior vena cava disclosed clorgyline-sensitive and resistant MAO activity, the latter being inhibited by semicarbazide but not by deprenyl or pargyline. No semicarbazide-sensitive species of MAO was found in human saphenous vein which also differed from the rat vasculature in that the predominant MAO activity was of the B type. It is concluded that kynuramine is also a good substrate for clorgyline-resistant enzymes and that rat vasculature may be a poor model for predicting deaminating mechanisms in human venous tissue.