Author(s): Siu GM, Draper HH
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Abstract The metabolism of malonaldehyde (MA) was investigated in vivo using male Wistar rats and in vitro using rat liver mitochondria. Twelve hr after intubation with [1,3-14C] MA, 60-70\%, 5-15\% and 9-17\% of administered radioactivity was recovered in expired CO2, feces and urine, respectively. In rats intubated with [1,2-14C) acetate, the corresponding values were 68-82\%, 1-2\% and 2.3\%. 14CO2 evolution was initially slower after 14C-MA administration than after 14C-acetate administration and more radioactivity was excreted in the feces and urine. In vitro experiments using [1,3-14C] MA showed that MA is metabolized primarily in the mitochondria via reactions involving O2 utilization and 14CO2 production. The apparent Km and Vmax were 0.5 mM and 9.3 nmol/min/mg protein for O2 uptake, respectively, and 2.0 mM and 2.4 nmol/min/mg protein for 14CO2 production. Addition of malonic acid to mitochondrial incubates at concentrations inhibitory to succinate dehydrogenase did not affect MA-induced O2 uptake but enhanced 14CO2 production from 14C-MA. 14C-Acetate appeared to be the major accumulating metabolite in rat liver mitochondrial preparations following a 120-min incubation with 14C-MA. A probable biochemical route for MA metabolism involves oxidation of MA by mitochondrial aldehyde dehydrogenase followed by decarboxylation to produce CO2 and acetate.
This article was published in Lipids
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