Cardiovascular Pharmacology Antiarrhythmic effect of acute oxygen-ozone administration to rats Clara Di Filippo a , Carmela Cervone a , Claudia Rossi b , Cristina di Ronza a , Raffaele Marfella c , Paola Capodanno b , Carlo Luongo b , Francesco Rossi a , Michele D'Amico a, ⁎ a Department of Experimental Medicine, Section of Pharmacology “L. Donatelli”, 2nd University of Naples, Italy b Department of Anaestesiological, Surgical and Emergency Sciences, 2nd University of Naples, Italy c Department of Geriatrics and Metabolic Diseases, 2nd University of Naples, Italy abstract article info Article history: Received 28 September 2009 Received in revised form 12 November 2009 Accepted 23 November 2009 Available online 1 December 2009 Keywords: Ozone Arrhythmias Ischemia Reperfusion Aconitine Potassium chloride (Rats) The antiarrhythmic effects of 100; 150; and 300 μg/kg i.p. oxygen/ozone mixture were tested on arrhythmias induced by i) ischemia; ii) ischemia/reperfusion; iii) aconitine (15 μg/kg/i.v.); potassium chloride (1.5% i.v.) in rats. 25 min of cardiac left descending coronary artery ischemia caused severe incidence of ventricular tachycardia, ventricular fibrillation and mortality. These were significantly reduced by pre-treatment of rats with oxygen/ozone mixture at doses of 150 and 300 μg/kg. In separate experiments using a protocol of 5 min ischemia followed by 8 min reperfusion this caused arrhythmias starting within 6 ± 1 s. The incidence of ventricular tachycardia was 100%, while ventricular fibrillation occurred in 75% of the animals and lasted 85 ± 14 s. The mortality was 62.5%. These figures were significantly (P b 0.01) reduced in animals treated with 150 μg/kg oxygen/ozone and a substantial increase observed with 300 μg/kg, whilst not affected by the lower dose of 100 μg/kg. 150 and 300 μg/kg oxygen/ozone prolonged the onset time for the appearance of arrhythmias induced by aconitine (300 μg/kg oxygen/ozone, ∼ 81% longer). Oxygen/ozone also reduced the ventricular tachycardia duration, ventricular fibrillation incidence, arrhythmia score, and increased the rat's survival rate. As for example, this latter was increased from 25% (aconitine) to 50% (aconitine + oxygen/ozone 150 μg/kg). 100 μg/kg oxygen/ozone was without effect. None of the oxygen/ ozone doses affected the arrhythmias caused by potassium chloride 1.5% i.v. All the oxygen/ozone antiarrhythmic effects were similar to those observed with lidocaine (1.5 mg/kg i.v.). In conclusion, oxygen/ozone has antiarrhythmic effects against arrhythmias caused by aconitine, myocardial ischemia and ischemia/reperfusion. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Cardiac arrhythmias are associated with a variety of drug treatments and heart diseases, such as heart failure and myocardial ischemia, and with genetic defects in seemingly healthy individuals (Sanguinetti and Bennett, 2003). Owing to relative inefficacy and side effects of currently available antiarrhythmic drugs, there is a continuing effort and need to develop cardioprotective compounds and treatments to cure this real channelopathy (Yang et al., 2007). Experimental and clinical evidences have proved advantageous effects of oxygen/ozone therapy in several pathologies characterized by a cellular oxidative and inflammatory burden, including renal injury, cardiopathy, atherosclerosis and septic shock (Romero Valdes et al., 1993; Hernandez et al., 1995; Bocci, 1996, 1999; Barber et al., 1999; Torossian et al., 2004; Qu et al., 2009). Oxygen/ozone administration has also been shown to beneficial in the prevention/ reduction of the myocardial tissue damage which follows an ischemic event (Di Filippo et al., 2008). In this context, however, no study has investigated until now the possible employment of oxygen/ozone mixture as an antiarrhythmic agent. For this purpose we undertook experiments in order to study the effects of acute oxygen/ozone mixture administration on two types of cardiac arrhythmias: i) generated by conditions of cardiac disorders such as myocardial ischemia and ischemia/reperfusion (I/R), and ii) those generated by cardiotoxic compounds. Myocardial ischemia and ischemia/reperfusion induced arrhyth- mias (e.g. ventricular tachycardia or ventricular fibrillation) are one of the most important causes of death in myocardial ischemia. Studies on anaesthetized rats have shown two distinct phases of post- occlusion ventricular arrhythmic activity (Parrat et al., 1981). The early phase of arrhythmias occurs within the first minutes of the occlusion, while the later phase of arrhythmias begins approximately hours after the occlusion or early after reperfusion. Overall these arrhythmias are caused by a burden of cytotoxic mediators released both during the ischemic and reperfusion phase, overwhelming the ionic balance and the normal functionality of the cardiac myocytes (Dhalla et al., 2000). European Journal of Pharmacology 629 (2010) 89–95 ⁎ Corresponding author. Department of Experimental Medicine, Section of Pharma- cology “L. Donatelli”, Second University of Naples, Via Costantinopoli 16, 80138 Naples, Italy. E-mail address: michele.damico@unina2.it (M. D'Amico). 0014-2999/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.ejphar.2009.11.061 Contents lists available at ScienceDirect European Journal of Pharmacology journal homepage: www.elsevier.com/locate/ejphar