Beta-oxidation of C-6-C-10 fatty acids in rat liver homogenates measured by selected ion monitoring: effects of cyanide and clofibrate.

The beta-oxidation of C-6-C-10-fatty acids/acyl CoA/acylcarnitines in whole rat liver homogenates was determined by specific and simultaneous measurements of the C-6-C-10-fatty acids, i.e. hexanoic, octanoic and decanoic acids, in hydrolysed homogenates in relation to time in assays incubated with the above-mentioned substrates. Measurements were performed by a combined gas chromatographic mass spectrometric technique, i.e. selected ion monitoring. The rate of beta-oxidation of the C-6-C-10-fatty acids/acyl CoA/acylcarnitines were registered as the consumption rate of the added substrate. The conversion to the C-2-shortened beta-oxidation products was illustrated simultaneously. The rate of beta-oxidation of C-6-C-10-fatty acids was several times higher in homogenates from clofibrate-treated rats than in control rats, both in the presence and absence of 2.0 mmol l-1 cyanide. Cyanide caused a minor but significant decrease in the beta-oxidation rate in both control and clofibrate-treated rats. No differences were found between the beta-oxidation of decanoic acid and decanoyl CoA in homogenates from clofibrate-treated rats, whereas the degree of beta-oxidation of DL-decanoylcarnitine was halved compared with decanoic acid and decanoyl CoA.