Partial characterization of monoamine oxidase in the salivary gland of rats.

Changes in the substrate specificity of monoamine oxidase in the rat submaxillary gland were examined after ligation of the excretory duct and after denervation by postganglionic sympathectomy. Atrophy of the parenchymal cells after ligation of the excretory duct was observed, but such was not so clear after the denervation. The rate of decreases in the enzyme activity after the duct ligation was highest with serotonin, intermediate with dopamine and tyramine and lowest with beta-phenylethylamine, used as substrates. The proportion of form A monoamine oxidase was examined using clorgyline as an inhibitor specific for form A enzyme; approximately 95%, 90% and 85% of the total enzyme activities were attributed to form A enzyme in the intact glands, in the denervated glands and in the duct ligated glands, respectively. These results indicate that 90% of the enzyme activity in the parenchymal cells and almost of all the enzyme activity in the sympathetic nerves of the gland may be attributed to form A enzyme and the atrophy of parenchymal cells after the duct ligation results in a decrease in form A enzyme more markedly than form B.