An interference study of the copper-induced plasma oxidizability test Sevgi Eskiocak a, ⁎ , Turan Ege b , Suleyman Bedir Yapar a , Sabriye Kaya a , Gulben Sayilan a a Department of Biochemistry, University of Trakya, Faculty of Medicine, Edirne, Turkey b Department of Cardiovascular Surgery, University of Trakya, Faculty of Medicine, Edirne, Turkey Received 12 April 2009; received in revised form 4 August 2009; accepted 19 August 2009 Available online 26 August 2009 Abstract Objectives: The aim of this study is to investigate the effect of cristaloid cardioplegic fluid (CCF) and its contents on the susceptibility of plasma to copper-catalyzed lipid peroxidation test. Design and methods: The plasma pool was divided into eight groups. Equal volumes of CCF or one of its contents were added to each group of the plasma pool. The accumulation of conjugated diene (CD) by copper-induced oxidation was monitored for a period of 5 h. Thiobarbituric acid-reactive substances (TBARS) formed during the incubation of plasma with copper was also measured. Results: It was found that, the production of CD and TBARS were inhibited and the lag time had increased, when the plasma was mixed with CCF or its contents. Conclusions: As a result, we conclude that that the susceptibility of plasma to copper-induced lipid peroxidation is interfered by CCF. The chloride ions, which major content of CCF, may play an important role on this effect. © 2009 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved. Keywords: Chloride ions; Conjugated diene; Copper-induced lipid peroxidation; Cristaloid cardioplegic fluid; Thiobarbituric acid-reactive substances Introduction Kontush et al. [1] reported that the oxidizability of plasma was correlated with the oxidizability of LDL isolated from the same plasma. The utilization of whole plasma, to characterize the oxidizability of plasma lipoprotein, offers several important advantages over the assays which use isolated lipoproteins, including the most common Cu(II)-based LDL oxidation assay [2]. During coronary bypass surgery, the myocardium is exposed to ischemia and reperfusion periods. We have previously reported that oxidative stress and myocardial tissue damage occurs as a result of a disturbance of the balance between reactive oxygen substances production and antioxidant defense during coronary bypass [3,4]. However, we have also found opposite results by using copper-induced plasma oxidizability test. We suggested that this situation in the copper-induced plasma oxidizability test may be interference [5]. We were focused on cristaloid cardioplegic fluid (CCF), which is used for reducing cardiac metabolism during surgery. Thus, the blood samples which are taken during coronary by-pass surgery contain CCF. Cristaloid cardioplegic fluid is an electrolyte rich fluid and it contains 0.11 M sodium chloride (NaCl), 1.19 mM calcium chloride (CaCl 2 ), 16 mM magnesium chloride (MgCl 2 ) and 16 M potassium chloride (KCl). Sodium bicarbonate (NaHCO 3 , 10 mM) is added to CCF immediately before use. We sought to investigate the effects of CCF and its contents on the susceptibility of plasma to copper-catalyzed lipid peroxidation. We aimed to show the interference of the CCF on the plasma lipid oxidizability test. We also aimed to reveal that, at which stage of lipid peroxidation, the inhibitory effect of CCF occurs and which one of the components of CCF has a role in this effect. Materials and methods Twenty healthy male volunteers (20.05 ± 1.57 years old) participated in this study. All the participants were non- smokers. They did not take medication or any antioxidant Available online at www.sciencedirect.com Clinical Biochemistry 42 (2009) 1728 – 1731 ⁎ Corresponding author. Fax: +90 2842352730. E-mail address: drseskiocak@yahoo.co.uk (S. Eskiocak). 0009-9120/$ - see front matter © 2009 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved. doi:10.1016/j.clinbiochem.2009.08.009