FORMATION OF PGF(2)-ISOPROSTANES DURING THE OXIDATIVE MODIFICATION OFLOW-DENSITY-LIPOPROTEIN

It has been recently reported that a series of prostaglandin F-2-like compounds (PGF(2) isoprostanes) are produced in vivo by non-enzymatic peroxidation of arachidonic acid. Of these, 8-epi-PGF(2 alpha) is the major component and has been shown to be a potent vasoconstrictor. Her e we investigated the formation of PGF(2)-isoprostanes during copper-m ediated oxidation of low density lipoprotein (LDL). Free and total (su m of free and esterified) levels of PGF(2)-isoprostanes were measured at times 0, 3, 6, 8 and 24 h, using a solid-phase extraction procedure and gas chromatography - mass spectrometry. In native LDL, free level s of PGF(2)-isoprostanes were between 0.06 and 0.10 ng/mg protein (n = 4), and the total levels ranged from 0.027 to 0.057 ng/mg protein (n = 4). Free levels of the isoprostanes were found to increase throughou t the oxidation, whereas total levels reached a maximum after 3 h then gradually decreased. 8-epi-PGF(2 alpha) was the major isoprostane for med (free concentration after 24 h 1.8 F 0.1 ng/mg protein (n = 4); to tal concentrations of 8.8 +/- 1.8 and 6.1 +/- 3.6 ng/mg protein (n = 4 ) after 3 and 24 h, respectively). The levels of isoprostanes correlat ed well with other indices of lipid peroxidation (conjugated dienes, h ydroperoxides, thiobarbituric reactive substances) measured at similar time points. The release of PGF(2)-isoprostanes from oxidised LDL in macrophages could be a contributory factor in the development of ather osclerosis. (C) 1994 Academic Press, Inc.