α- Tocopherol Binding Activity of Red Blood Cells in Smokers

Abstract

Despite high plasma levels of vitamin E, red blood cell membranes contain relatively low levels of vitamin E. This suggests the existence of a selective vitamin E uptake/regeneration system in human red blood cell membranes. α-Tocopherol binding sites on human red blood cells are thought to be involved in the uptake of α-tocopherol from the plasma. To understand the role of the uptake system we have compared the α-toco-pherol content and binding activity of red blood cells from smokers and non-smokers. The specific binding of [³H]α-tocopherol to pure red blood cell preparations from smokers (n = 7, 28.4 ± 2.8 years) was 30.6 ± 3.2 fmoles per 3 × 10⁸ red blood cells and for non-smokers (n = 17, 27.9 ± 1.3 years) was 41.7 ± 3.7 fmoles per 3 × 10⁸ red blood cells. Thus a-tocopherol uptake activity was significantly lower in smokers (P = 0.05). Red blood cells from smokers contained less (1.8 ± 0.4 μg/gHb) α-tocopherol than non-smokers (2.8 ± 0.3 μg/gHb), (P < 0.05), despite plasma levels of α-toco-pherol being similar: 12.9 ± 0.8 μM in non-smokers vs. 12.7 ± 0.5 μM in smokers. However, adjusting plasma α-tocopherol for total plasma cholesterol plus triacyl-glycerols showed α-tocopherol levels were higher (P < 0.01) in non-smokers (2.84 ± 0.10 μmol α-tocopherol/ mmol [cholesterol+triacylglycerol]) than in smokers (2.36 ± 0.11 μmol α-tocopherol/mmol [cholesterol+triacylglycerol]). The reduced α-tocopherol levels in red blood cells from smokers may be due to impairment of α-tocopherol uptake activity. The reduced levels of α-tocopherol in smokers red blood cells was not associated with any changes in cell membrane fluidity. At present it is not known whether supplementation of smokers with vitamin E would normalise the α-tocopherol uptake activity of red blood cells.

Key Words:

• Smoking
• α-tocopherol uptake
• red blood cells
• α-tocopherol
• membrane fluidity