Interaction of aromatic aldehydes with isolated rat liver mitochondria

It has been suggested that aromatic aldehydes may reduce cytochrome c [Wolf et al. Fedn Proc. 39 (3), 1013 (1980)]. Therefore, interaction of the aromatic aldehydes, p-anisaldehyde, benzaldehyde, p-tolualdehyde, p-carboxybenzaldehyde, p-chlorobenzaldehyde and p-nitrobenzaldehyde, with rat liver mitochondria was examined in vitro. Although both pyruvate/malate- and succinate-mediated respiration, as well as that mediated by other citric acid cycle intermediates, were inhibited by the aromatic aldehydes (0.5 to 1.0 mM), cytochrome c oxidase was not inhibited by aromatic aldehydes (1.0 to 20 mM). There was a marked inhibition of succinic dehydrogenase and both ADP- and DNP-stimulated respiration by benzaldehyde (2 to 20 mM). Since both pyruvate/malate- and succinate-mediated respiration were inhibited by the aromatic aldehydes without inhibition of cytochrome c oxidase, several sites of inhibition, possibly both at the site of transport of substrates and the active enzymes, may exist. Benzaldehyde, 300 microM, inhibited pyruvate/malate-mediated state 3 respiration by 50% which suggests that no additional functional group or metabolism to another species is required for these inhibitory effects.