Determination of choline and ethanolamine plasmalogens in human plasma by HPLC using radioactive triiodide (1-) ion (125I3-).
For the purpose of developing highly sensitive and convenient determination of plasmalogens, the high-performance liquid chromatography (HPLC) method using radioactive iodine ((125)I) was investigated. Radioactive triiodide (1-) ion ((125)I(3)(-)), which is an actual iodine form capable of reacting with vinyl ether bond ([bond]CH(2)[bond]O[bond]CH[double bond]CH[bond]) of plasmalogens, could be safely and efficiently produced by oxidizing a commercial radioactive sodium iodine (Na(125)I) with hydrogen peroxide (H(2)O(2)) under acid condition (pH 5.5-6.0), which is called iodine-125 reagent. I(3)(-) specifically reacted with plasmalogens at the molar ratio of 1:1 in methanol, and 1 or 2 mol of plasmalogens was involved in the binding with iodine per iodine atom, resulting in the formation of stable iodine-binding phospholipids. The HPLC system with Diol column and acetonitrile/water as a mobile phase was available for separating iodine-binding phospholipids from nonbinding free iodine and for separately eluting iodine-binding phospholipids derived from choline and ethanolamine plasmalogens. Using iodine-125 reagent (1.85 MBq/ml), plasmalogens were detectable at high sensitivity of 10,000-15,000 cpm/nmol, which is more than 1000-fold higher sensitivity than the classical determination with nonradioactive iodine. Plasmalogen concentrations in human plasma were measured with the HPLC system and determined as, on average, 129.1+/-31.3 microM (n=8) in a 1.2 content ratio of choline to ethanolamine plasmalogens, a concentration that nearly agrees with the value reported previously.
Maeba
Ryouta
R
Department of Biochemistry, Teikyo University School of Medicine, 2-11-1 Kaga, Itabashi-Ku, Tokyo 173-8605, Japan. maeba@med.teiyko-u.ac.jp
Ueta
Nobuo
N
D002794:Choline / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid; D019856:Ethanolamine / Q000032:analysis*; D006801:Humans; D006861:Hydrogen Peroxide / Q000737:chemistry; D007455:Iodine / Q000737:chemistry*; D007457:Iodine Radioisotopes / Q000737:chemistry; D010084:Oxidation-Reduction; D010949:Plasma / Q000737:chemistry*; D010955:Plasmalogens / Q000032:analysis*; D014753:Vinyl Compounds / Q000737:chemistry
D007457:Iodine Radioisotopes; D010955:Plasmalogens; D014753:Vinyl Compounds; C100195:vinyl ether; D019856:Ethanolamine; D007455:Iodine; D006861:Hydrogen Peroxide; D002794:Choline