ANTIOXIDANT AND PROOXIDANT EFFECTS OF EPINEPHRINE AND ISOPRENALINE ONPEROXIDATION OF LDL AND LIPID LIPOSOMES

Antioxidant or pro-oxidant properties of epinephrine (EPI) and isopren aline (ISO) were studied in the absence and presence of Fe2+, Fe3+ and Cu2+ ions. EPI and ISO (>2 mu mol/l) inhibited peroxidation of low de nsity lipoprotein (LDL) induced by 2, 2'-azobis(2-amidino-propane) (AA PH). EPI had a similar inhibitory potency as ISO, but their potency wa s several times higher than the potency of alpha-tocopherol (alpha-TOC ). When the LDL peroxidation was induced by 5 mu mol/l CuSO4, EPI and ISO enhanced LDL peroxidation at low concentrations (10 mu mol/l) and decreased peroxidation at higher concentrations (30 mu mol/l). The com pounds had a similar tendency to inhibit the peroxidation of phosphati dylcholine liposomes. EPI (3-30 mu mol/l) inhibited lipid peroxidation of phosphatidylcholine liposomes induced by 2 mmol/l of AAPH, but it was less effective and even increased the peroxidation, when the sampl es contained 2 mmol/l AAPH with 50 mu mol/l FeSO4 or 2 mmol/l AAPH wit h 20 mu mol/l FeCl3. Inhibition of lipid peroxidation by EPI was also observed when studying decreased oxygen consumption, when the peroxida tion of linoleic acid was induced by lipoxidase. In conclusion, EPI an d ISO reduced lipid peroxidation, but they exhibit pro-oxidant propert ies in the presence of Fe2+, Fe3+ or Cu2+ ions, depending on the catec holamine and ionic concentration.