Selective measurements of phospholipid peroxidation in ischaemic, reperfused and oxygen radical perfused isolated rat hearts

J Mol Cell Cardiol 22 (Supplement 111)(1990) J='S~SELECTIVH NEASUREWENTSOF PHOSPHOLIPID PEROXIDATION IN ISCHAENIC, RRPERFUSNDANDOXYGNNRADICALPHRFUSEDISOLATHDRAT HEARTS Anna-C. Hegstad, Harald Strand, Kirsti Ytrehus. Department of Medical Physiology, University of Tromse, Norway. Peroxidation of membrane polyunsaturated fatty acids is a proposed mechanism for postischaemic myocardial dysfunction. Control Langendorff-perfused (n=5)r ischaemic (60 min, n=6), reperfused (2 min, n=6 and 10 min, n=4) or oxygen radical perfused hearts (hypoxanthine plus xanthine oxidase 0.025 U/ml, n=4) were freeze-clamped and homogenized in liquid nitrogen. Lipid extraction and separation of phospholipids were performed before enzymatic hydrolysis with phospholipase AZ. Reverse-phase HPLC was used to separate hydroperoxyand hydroxyfatty acids from unoxidized fatty acids. The degree of peroxidation was estimated by UV abs (235nm, conjugated diens). Ischaemia and oxygen radicals resulted in increased levels when compared to controls (49*7 and 58*9 vs 31*6 units/ mg dry wt). Levels in 2 and 10 min reperfused hearts were unchanged from controls (30*3 and 3522 units/ mg dry wt). This indicates that 60 min ischaemia induce peroxidation and that reperfusion may result in release of lipid oxidation products from the membran and further degradation.

pS89IS NALONDIALDRHYDEA NARXHROF THE EFFECT OF OXYGENFREE RADICALS IN RAT HEART TISSUE? George Ballagi-Pordany', Jiirgen Richter2, Maria 2s. Koltai' Zoltan Aranyi', Gabor Pogatsa', Wolfgang Schaper'. 'National Institute'of Cardiology, Budapest, Hungary; 2Max-Planck-Institute, Bad Nauheim, FRG We found no evidence for increased malondialdehyde (MDA) production during Ht02 and purine derived free radical perfusion or ischemia and reperfusion in isolated buffer-perfused rat heart or in effluent buffer in contrast to several authors. Free radicals also did not change coronary flow, heart rate or rhythm except at 1.2 mM H,O,, where the tissue MDA content was increased in contrast to the other investigated groups, perhaps reflecting the toxicity associated with such non-physiologic concentration of H202. In the generally used thiobarbituric acid (TBA) assay the trichloracetic acid/HCl media, the shorter reaction time, the detection of developed colour in aquous solution, the lack of an absorption maximum of this colour at 532 nm versus the TBA assay that specifically measures MDA, developed by Ohkawa et al, and used in our experiments, may explain the difference between our and other authors' results. We concluded that MDA is not a primary and direct lipidperoxidation product of exogenous or endogenous oxygen free radicals. psgo

ME~RE~EMT Claudia Chair

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