diphenylhexatriene and dihydrolipoic-acid

Fluorescence anisotropy (r) was determined in hypoxic/reoxygenating rat heart mitochondria by means of 1,6-diphenyl-1,3,5-hexatriene. During hypoxia, values for r increased, indicating a rigidified membrane. Membrane fluidity was increased when 20 pmol to 2 nmol/mg protein of dihydrolipoic acid (DHL) was present during hypoxia. Dithiothreitol (DTT) or 2-mercaptopropionylglycin (MPG) at similar concentration did not result in membrane fluidization under these conditions. Peroxidative damage was induced in mitochondria by H2O2. In the presence of 2 nmol/mg protein of DHL, malondialdehyde production was decreased by 50%. DTT or MPG brought about only a 25% decrease. These results were corroborated by spin label studies with 4-maleimido-TEMPO and 5-proxylnonane (5-P-9); H2O2 induced a decrease in fluidity in the region of labeled thiol groups and an increase in polarity sensed by 5-P-9. DHL proved efficient in reducing such fluidity and polarity changes.

Topics: Animals; Cyclic N-Oxides; Diphenylhexatriene; Disulfides; Dithiothreitol; Electron Spin Resonance Spectroscopy; Fluorescence Polarization; Hydrogen Peroxide; Intracellular Membranes; Lipid Peroxidation; Male; Malondialdehyde; Membrane Fluidity; Mitochondria, Heart; Oxygen; Pyrrolidines; Rats; Rats, Inbred Strains; Rats, Wistar; Spin Labels; Thioctic Acid; Tiopronin