methyl-13-hydroperoxy-9-11-octadecadienoate and linoleic-acid-hydroperoxide

Formation of fluorescence by the reaction of various amino acids with lipid hydroperoxides, i.e., linoleic acid 13-monohydroperoxide, methyl linoleate 13-monohydroperoxide and phosphatidylcholine hydroperoxide, in the presence of methemoglobin was investigated. Two types of fluorescence were produced: fluorescent dityrosine (3,3'-dityrosine) from tyrosine, and unidentified fluorophores with alpha- and epsilon-amino groups of various amino acids. While the former was stable after treatment with borohydride, the latter fluorophores were readily destroyed. The rate of dityrosine formation was rapid, and the yield of dityrosine was dependent on the concentrations of tyrosine and the lipid hydroperoxides. Butylated hydroxytoluene and tocopherol inhibited the formation of dityrosine, but did not affect the formation of fluorophores on the amino groups. Dityrosine appears to be formed by radical reaction of the lipid hydroperoxides, while the other fluorophores seem to be created by nonradical mechanisms.

Topics: Amino Acids; Borohydrides; Butylated Hydroxytoluene; Fluorescent Dyes; Kinetics; Linoleic Acids; Lipid Peroxides; Luminescent Measurements; Methemoglobin; Models, Chemical; Phosphatidylcholines; Spectrometry, Fluorescence; Tyrosine; Vitamin E

Linoleate monohydroperoxide (L-HPO), methyl linoleate monohydroperoxide (ML-HPO), and methyl hydroperoxy-epoxy-octadecenoate (ML-X) inhibited state 3 respiration of mitochondria when palmitate, palmitoyl CoA, or L-palmitoylcarnitine was used as a substrate. L-HPO was the most effective, and 50% inhibition of palmitate-supported respiration was observed with 2, 3.3, and 6.5 nmol/mg protein of L-HPO, ML-X, and ML-HPO, respectively. Almost the same values were obtained when palmitoyl CoA or L-palmitoylcarnitine was used in place of palmitate. L-HPO inhibited the reaction of beta-oxidation in mitochondria in a similar concentration range (4 nmol/mg protein for 50% inhibition) when L-palmitoylcarnitine was used as a substrate. L-HPO also inhibited the formation of 3-hydroxypalmitoylcarnitine from the same substrate. Carnitine palmitoyltransferase activity of mitochondria was inhibited by L-HPO, 50% inhibition occurring at 12 nmol/mg protein. These inhibitory effects of L-HPO were weaker when ATP was removed by hexokinase and glucose. ATP-dependent formation of carnitine ester of L-HPO was also suggested. It was deduced that L-HPO (and ML-X and ML-HPO after hydrolysis) was converted to carnitine ester and inhibited the palmitate metabolism at the site(s) of intramitochondrial carnitine palmitoyltransferase (and possibly acyl CoA dehydrogenase).

Topics: Animals; Carnitine O-Palmitoyltransferase; Chromatography, Thin Layer; Epoxy Compounds; In Vitro Techniques; Linoleic Acids; Lipid Peroxides; Male; Mitochondria, Liver; Oxidation-Reduction; Palmitates; Palmitic Acids; Rats

Linoleate hydroperoxide and linoleate at concentrations of 100-140 nmol-mg protein activated state 4 respiration of rat heart mitochondria 4.2-fold, increased the apparent enthalpy change of the respiration per gram atom of oxygen consumed from -148 to -226 kJ/O and completely inhibited oxidative phosphorylation. Methyl linoleate hydroperoxide or methyl linoleate did not show the same effects. Further addition of linoleate hydroperoxide or linoleate induced oligomycin-insensitive Mg-ATPase to a level 5 or 2 times, respectively, that obtained with 120 muM dinitrophenol, accompanied by clearing of the mitochondrial suspension and release of malate dehydrogenase from the matrix. Methyl linoleate hydroperoxide had the same effects except that the induced Mg-ATPase activity retained oligomycin sensitivity. Methyl linoleate did not show either effect.

Topics: Adenosine Triphosphatases; Animals; Calorimetry; Dose-Response Relationship, Drug; Enzyme Activation; Linoleic Acids; Lipid Peroxides; Magnesium; Male; Mitochondria, Heart; Oxidative Phosphorylation; Oxygen Consumption; Rats