Abstract
In control rats, long-chain monocarboxylyl-CoA, ω-hydroxymonocarboxylyl-CoA, and dicarboxylyl-CoA esters were substrates for hepatic, renal, and myocardial peroxisomal β-oxidation. The latter enzyme system could not be detected in skeletal muscle. Clofibrate treatment resulted in an enhancement of peroxisomal β-oxidizing capacity in various tissues. Intact mitochondria from control rat liver and kidney cortex incubated in the presence of L-camitine were capable of oxidizing long-chain monocarboxylyl-CoAs and ω-hydroxymonocarboxylyl-CoAs but not dicarboxylyl-CoAs. However, control rat liver mitochondria permeabilized by digitonin oxidized dodecanedioyl-CoA indicating that the liver mitochondrial β-oxidation system can act on dicarboxylyl-CoA esters even if the overall intact mitochondrial system is inactive on these substrates. Intact liver mitochondria ffom clofibrate-treated animals rapidly oxidized lauroyl-CoA and 12-hydroxylauroyl-CoA but not dodecanedioyl-CoA. These mitochondria were active on hexadecanedioyl-CoA and this activity amounted to 20-25%of that measured with palmitoyl-CoA and 16-hydroxypalmitoyl-CoA as substrates. No mitochondrial dicarboxylyl-CoA oxidation could be detected in kidney cortex from animals receiving clofibrate in their diet. Heart and skeletal muscle illtact mitochondria from untreated and clofibrate-treated rats were capable of oxidizing each type of acyl-CoA as a substrate. Dicarboxylyl-CoA synthetase and camitine dicarboxylyltmnsfbrase activities were detected in various tissues from untreated and clo6brate-treated rats with the exception of carnitine dodecanedioyltransfbrase reaction in livers ffom untreated and ciofibrate-treated rats. In skeletal muscle, the acyl-CoA synthetase activities could be detected only in the presence of detergents.
