INTRAMITOCHONDRIAL DISTRIBUTION OF THREE ACYL-COA DEHYDROGENASES IN RAT LIVER PARENCHYMAL CELLS REVEALED BY QUANTITATIVE IMMUNOELECTRON MICROSCOPY

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Intramitochondrial distribution of three acyl-CoA dehydrogenases in parenchymal cells of rat liver was investigated by means of a post-embedding immunocytochemical technique. Vibratome sections of rat liver fixed with 4% formaldehyde+1% glutaraldehyde were embedded in Lowicryl K4M at -20°C. Ultrathin sections were incubated with antibodies against short-chain acyl-CoA dehydrogenase (SCAD), medium-chain acyl-CoA dehydrogenase (MCAD), and long-chain acyl-CoA dehydrogenase (LOAD), respectively, followed by a protein A-gold complex. The gold particles representing the antigenic sites for three acyl-CoA dehydrogenases were present exclusively in mitochondria. Quantitative analysis of labeling density confirmed that the labeling density for the enzymes was significantly high in the mitochondria. The histogram analyzing the distribution pattern demonstrated that the most of the gold particles were found in zone with a width of approximately 12nm along the innermembrane. The results suggested that mitochondrial acyl-CoA dehydrogenases are associated with the mitochondrial innermembrane.