A comparison of the in vitro binding of alpha-tocopherol to microsomes of lung, liver, heart and brain of the rat.
The in vitro binding of alpha-tocopherol to microsomes of lung, liver, heart and brain of the rat was studied with the insoluble tocopherol ligand presented as a complex with bovine serum albumin. Under these conditions, all microsomes showed nonsaturable binding of alpha-tocopherol and the amount bound to microsomes was linearly proportional to the concentration of albumin-complexed tocopherol. Increasing the amount of alpha-tocopherol bound to microsomes in this manner reduced the extent of lipid peroxidation induced by added ferrous iron. The apparent affinities of the microsomes for alpha-tocopherol, as indicated by the amount bound at a given concentration of albumin-complexed tocopherol, decreased in the order brain greater than liver approximately equal to heart greater than lung. The differences in affinity did not correlate with total fatty acid content (r = -0.39), total unsaturated fatty acid content (r = -0.26), or with the content of fatty acids containing two or more double bonds (r = -0.01). A high positive correlation was found with the content of fatty acids containing three or more double bonds (r = +0.96). Since lung microsomes contain approx. 6-times the tocopherol levels of liver and brain and about twice that of heart microsomes, these results show that the in vivo levels of microsomal tocopherol do not reflect microsomal affinity for this biological antioxidant.
D000818:Animals; D001921:Brain / Q000378:metabolism*; D055598:Chemical Phenomena; D002621:Chemistry; D005227:Fatty Acids / Q000378:metabolism; D007700:Kinetics; D008054:Lipid Peroxides / Q000378:metabolism; D008168:Lung / Q000378:metabolism*; D008297:Male; D008861:Microsomes / Q000378:metabolism*; D008862:Microsomes, Liver / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism*; D051381:Rats; D013329:Structure-Activity Relationship; D014810:Vitamin E / Q000378:metabolism*
D005227:Fatty Acids; D008054:Lipid Peroxides; D014810:Vitamin E