Figure 3.

α-TQH₂ efficiently and stoichiometrically reduces CoQ₁₀ present in intact LDL but not LDL lipid extracts or organic solution. (A) In vivo CoQ₁₀H₂-enriched (30) LDL (1.1 μM in apoB) was allowed to autoxidize until all of the coenzyme Q was present as CoQ₁₀. The intact lipoprotein (○), its total lipid extract (▵), or an ethanolic solution of CoQ₁₀ (□) were then placed on ice before 10 μM of α-TQH₂ was added. The samples were placed at 37°C and aliquots were removed at the time points indicated and analyzed for CoQ₁₀H₂. The initial CoQ₁₀ concentration was 3.1 ± 0.25, 2.62 ± 0.20, and 10 ± 0 μM (mean ± SD; n = 3) for intact LDL, LDL lipid extract, and organic CoQ₁₀ solution, respectively. The data shown are average values derived from three independent experiments with <3% variation for all conditions. (B) In vivo CoQ₁₀H₂-enriched (29) LDL (0.93 μM in apoB) was preincubated at 37°C for ≈8 hr and then left at room temperature overnight for most of the CoQ₁₀H₂ to autoxidize. Such LDL preparation contained 0.3 and 3 μM of CoQ₁₀H₂ and CoQ₁₀, respectively, and was hydroperoxide-free as determined by HPLC (see text). Increasing amounts of α-TQH₂ were then added and the formation of CoQ₁₀H₂ monitored at 37°C. The data shown are mean values derived from a single experiment performed in triplicate, with variation <5%.