Characterization of cellular uptake and distribution of coenzyme Q10 and vitamin E in PC12 cells

Coenzyme Q (CoQ) is a well-known electron transporter in the mitochondrial respiratory chain. Furthermore, ubiquinol (UQH(2)) - a reduced form of ubiquinone (UQ) - has been shown to act as a radical-scavenging antioxidant. Some studies have reported the beneficial effect of CoQ addition to cultured cells; however, the cellular uptake and distribution of CoQ have not been elucidated. In the present study, we used rat pheochromocytoma PC 12 cells to investigate and compare the cellular uptake and distribution of CoQ(10) and alpha-tocopherol (alpha T). UQ(10) or UQ(10)H(2) treatment resulted in an increase in the cellular content of both CoQ(10) in a time- and concentration-dependent manner. A subcellular firactionation study revealed that the added UQ(10) as well as UQ(10)H(2) mainly localized in the mitochondrial fraction, which is similar to the localization of endogenous CoQ but different from that of alpha T. The cellular distribution of alpha T directly corresponded to the lipid distribution, while the CoQ distribution did not show any relationship with the lipid distribution, particularly in the mitochondrial and microsomal fractions. These results indicate that the cellular distribution of CoQ is completely different from that of alpha T; moreover, a certain system which accumulates CoQ preferentially in mitochondria may be suggested. (C) 2009 Elsevier Inc. All rights reserved.