Effects of idebenone on the composition of brain synaptosomal membranes of rats

Male and female CFY rats of 21 months of age were treated per os by 50 mg idebenone per kg body weight/day for 5 weeks while the controls received only the solvent. Synaptosomal fractions of the brain cortex were prepared and tested as follows: (1) Labeling by 1,6-diphenyl-1,3,5-hexatriene (DPH) and the fluorescence anisotropy (r) of this label was measured at various optical densities. The average values of r extrapolated to zero optical density were 0.1831 +/- 0.0025 in the control group and 0.1854 +/- 0.0019 in the idebenone-treated animals; the difference is statistically not significant. (2) Labeling with 3 different spin labels (5-NS, N-oxyl-4', 4'-dimethyloxazolidine derivative of stearic acid with the doxyl groups in C-5; 16-NS, the same derivative of stearic acid with the doxyl groups in C-16 position; and MAL-SL, 3-maleimido-2,2,5,5-tetramethyl-1-pyrrolidinyloxy). Routine ESR spectroscopy was applied to characterize the molecular motion of these labels in their microenvironment. These spin labels did not display any significant change in their environment under the influence of idebenone treatment. (3) Protein contents of the samples were measured and samples of synaptosomes containing 3.5 mg protein were dissolved in 1% Na(Dod)SO4 + 1% beta-mercaptoethanol and boiled for 2 min, then elaborated by gel filtration chromatography on a column of sepharose 2B. The elution fluid was collected in separate fractions of 1 ml volume and their protein content was estimated by measuring the absorbance at 280 nm. Distribution histogram of the protein fractions revealed no difference between the placebo- and verum-treated animals. These studies demonstrate that in vivo application of idebenone does not alter the composition of synaptosomal membranes.