Metabolic depropargylation and its relationship to aldehyde dehydrogenase inhibition in vivo

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Abstract
The relationship between metabolic depropargylation in vitro to inhibition of the low Km aldehyde dehydrogenase (AlDH) of rat liver mitochondria in vivo was determined for a number of compounds bearing a propargyl substituent on N2 or O2. Only those compounds which enzymatically released the highly reactive .alpha.,.beta.-acetylenic aldehyde, propiolaldehyde, when incubated in vitro with phenobarbital-induced rat liver microsomes, e.g., tripropargylamine, pargyline and N-propargylbenzylamine, significantly elevated blood acetaldehyde levels when administered in vivo. Mitochondrial AlDH activity in these animals was correspondingly reduced to .ltoreq. 20% that of control animals. Compounds that did not inhibit mitochondrial AlDH activity to this degree did not produce significant levels of propiolaldehyde when incubated with microsomes. For this series of compounds, metabolic depropargylation is a requirement for AlDH inhibitory activity in vivo.