Coenzyme Q10 in plasma and erythrocytes:: comparison of antioxidant levels in healthy probands after oral supplementation and in patients suffering from sickle cell anemia

Background: The membrane-associated antioxidant coenzyme Q(10) (CoQ(10)) or ubiquinone-10 is frequently measured in serum or plasma. However, little is known about the total contents or redox status of CoQ(10) in blood cells. Methods: We have developed a method for determination of CoQ(10) in erythrocytes. Total CoQ(10) in erythrocytes was compared to the amounts of ubiquinone-10 and ubihydroquinone-10 in plasma using high-pressure liquid chromatography (HPLC) with electrochemical detection and internal standardisation (ubiquinone-9, ubihydroquinone-9). Results: Investigations in 10 healthy probands showed that oral intake of CoQ(10) (3 mg/kg/day) led to a short-term (after 5 h, 1.57 +/- 0.55 pmol/mul plasma) and long-term (after 14 days, 4.00 +/- 1.88 pmol/mul plasma, p < 0.05 vs. -1 h, 1.11 +/- 0.24 pmol/mul plasma) increase in plasma concentrations while decreasing the redox status of CoQ(10) (after 14 days, 5.37 +/- 1.31% in plasma, p < 0.05 vs. -1 h, 6.74 +/- 0.86% in plasma). However, in these healthy probands, CoQ(10) content in red blood cells remained unchanged despite excessive supplementation. In addition, plasma and erythrocyte concentrations of CoQ(10) were measured in five patients suffering from sickle cell anemia, a genetic anemia characterised by an overall accelerated production of reactive oxygen species. While these patients showed normal or decreased plasma levels of CoQ(10) with a shifting of the redox state in favour of the oxidised part (10.8-27.2% in plasma), the erythrocyte concentrations of CoQ(10) were dramatically elevated (280-1093 pmol/10(9) ERY vs. 22.20 +/- 6.17 pmol/10(9) ERY). Conclusions: We conclude that normal red blood cells may regulate their CoQ(10) content independently from environmental supplementation, but dramatic changes may be expected under pathological conditions. (C) 2002 Elsevier Science B.V. All rights reserved.