Figure 1.

Hydroquinones protect LDL’s cholesteryl esters from ROO^⋅-induced peroxidation. An LDL solution (1.2 μM in apoB) was incubated at 37°C with 2 mM of AAPH in the absence (A) or presence (B) of 10 μM of 2,5-DTBHQ or α-TQH₂ (C). At the time points indicated, aliquots were taken and analyzed for CoQ₁₀H₂ (▪), CoQ₁₀ (□), α-TOH (○), and CE-O(O)H (⊞) and, where applicable, for α-TQH₂ (▴) and α-TQ (▵). The data shown represent mean values of three separate experiments with a variation of <15%. The initial concentrations of CoQ₁₀H₂, CoQ₁₀, and α-TOH in the LDL solution were 0.73 ± 0.15, 0.43 ± 0.09, and 9.5 ± 0.9 μM, respectively. The initial levels of α-TQH₂ and α-TQ measured after addition of the freshly prepared hydroquinone to LDL varied between 8.9 to 9.1 and 1.1 to 1.6 μM, respectively. Note that the sum of CoQ₁₀H₂ plus CoQ₁₀ and that of α-TQH₂ plus α-TQ represent 100%.