Abstract

The biochemical effect of nitroglycerin on myocardial monoamine oxidase (MAO) activity was studied in vivo and in vitro. Nitroglycerin administered in vivo inhibited significantly the MAO activity of rat heart mitochondria with tyramine as substrate. Nitroglycerin also inhibited MAO activity of rat heart mitochondria in vitro with both tyramine and tryptamine as substrates. The mechanism of the inhibition of the MAO activity by nitroglycerin was studied in vitro on a solubilized and partially purified mitochondrial monoamine oxidase. The effect of nitroglycerin on the enzyme kinetics of MAO indicated that the drug acts as competitive inhibitor of MAO. A significant inhibition of rat liver and brain MAO activity was also observed in the presence of nitroglycerin. The effect of nitroglycerin on MAO activity was compared to that of other organic nitrates, but no correlation was observed between the number of nitrate groups per molecule and the molar inhibitory action.