Inhibition of rat heart mitochondrial electron transport in vitro: implications for the cardiotoxic action of allylamine or its primary metabolite, acrolein.

Allylamine (3-aminopropene) is a specific cardiac toxicant that causes aortic, valvular and myocardial lesions in many species. Myocardial necrosis can be observed 24 h after a single dose. Acute toxicity is believed to involve metabolism of allylamine to highly reactive acrolein (2-propenal). Allylamine has been shown to bind to mitochondria from aorta and heart, suggesting that the subcellular site of injury is at or near the mitochondrion. The present investigation compared the effect of allylamine and its primary metabolite, acrolein, on electron transport and oxidative phosphorylation in mitochondria isolated from rat heart (RHM). Both compounds weakly inhibited mitochondrial electron transport with either the combination of glutamate, malate, and malonate (GMM, NADH-linked) or succinate as substrate. Comparisons of the slopes of concentration-effect regression (range of concentrations tested, 0.20-2.0 mM) lines showed acrolein to have significantly greater inhibitory effects than allylamine (range of concentrations tested, 0.22-6.4 mM) on GMM oxidation, while no significant difference in the abilities of the compounds to inhibit succinate oxidation were observed, indicating site preferences for inhibitory action. The addition of an uncoupling agent could not reverse inhibition with either substrate system. These results indicate that both the parent compound and its proposed metabolite primarily inhibit electron transport with little direct effect on the coupling mechanism. The State III EC50 (effective concentrations for 50% inhibition of control mitochondrial enzyme activities) for allylamine (2.29 mM with succinate as substrate and 1.22 mM with GMM) and acrolein (0.80 mM with succinate as substrate and 0.39 mM with GMM) are probably too great to invoke the direct action of either the parent compound or its oxidized metabolite on mitochondrial electron transport as a primary mechanism in the cardiotoxic action of allylamine.