title: The protective effect of heat stress against reperfusion arrhythmias in the rat.
abstract: Heat stress provides protection against mechanical dysfunction and myocardial necrosis after prolonged ischemia. We have investigated whether this protection extends to reperfusion arrhythmias occurring after a short (non-lethal) ischemic insult. Anaesthetized open chest rats were subjected to a 5-min occlusion of the left coronary artery. The incidence and duration of reperfusion arrhythmias and the duration of sinus rhythm were assessed in the first 5 min of reperfusion. Prior heat stress led to a reduction in the incidence (100-63%, P < or = 0.05) and duration (66.2 +/- 15.8 to 9.4 +/- 2.9 s, P < or = 0.05) of ventricular tachycardia and a non-significant reduction in the incidence (76-50%) and duration (74.3 +/- 23.4 to 42.9 +/- 24.4 s, P = 0.09) of ventricular fibrillation. This resulted in a significant increase in the duration of sinus rhythm (142.1 +/- 27.6 to 216.7 +/- 24.8 s, P < or = 0.05) and reduction in arrhythmia score (P < or = 0.05) in heat stressed rats compared with controls. This protection against reperfusion arrhythmias was associated with a two-fold increase in endogenous catalase activity and expression of the inducible heat stress protein HSP 70. Inhibition of catalase with pre-administered 3-amino triazole resulted in a paradoxical protection in both sham and heat stress hearts. We conclude that heat stress leads to protection against reperfusion arrhythmias; however, we have been unable to resolve whether the changes in catalase activity or HSP expression are the mediators of the demonstrated cardioprotection.
authors.affiliation: Hatter Institute for Cardiovascular Studies, University College Hospital, London, UK.
authors.forename: S E
authors.initials: SE
authors.lastname: Steare
authors.forename: D M
authors.initials: DM
authors.lastname: Yellon
mesh_terms: D000640:Amitrole / Q000494:pharmacology; D000818:Animals; D002374:Catalase / Q000037:antagonists & inhibitors / Q000502:physiology; D003327:Coronary Disease / Q000150:complications; D003404:Creatinine / Q000097:blood; D006360:Heat-Shock Proteins / Q000502:physiology; D006358:Hot Temperature; D015428:Myocardial Reperfusion Injury / Q000517:prevention & control*; D009206:Myocardium / Q000473:pathology; D009336:Necrosis; D011188:Potassium / Q000097:blood; D051381:Rats; D012964:Sodium / Q000097:blood; D013312:Stress, Physiological / Q000503:physiopathology*; D017180:Tachycardia, Ventricular / Q000097:blood / Q000517:prevention & control*
chemical_list: D006360:Heat-Shock Proteins; D012964:Sodium; D003404:Creatinine; D002374:Catalase; D011188:Potassium; D000640:Amitrole