Sex influences the susceptibility to reperfusion-induced sustained ventricular tachycardia and beta-adrenergic receptor blockade in conscious rats.
Reperfusion after a brief period of cardiac ischemia can lead to potentially lethal arrhythmias. Importantly, there are sex-related differences in cardiac physiology and in the types and severity of cardiac arrhythmias. Therefore, we tested the hypothesis that gonadal hormones influence the susceptibility to reperfusion-induced sustained ventricular tachycardia (VT), as well as the response to beta-adrenergic receptor blockade. Male and female intact and gonadectomized rats were instrumented, and arterial pressure, temperature, ECG, and cardiac output were recorded. In addition, a snare was placed around the left main coronary artery. Tension was applied to the snare for determination of susceptibility to sustained VT produced by 3 min of occlusion and reperfusion of the left main coronary artery in conscious rats. Reperfusion culminated in sustained VT in 77% (10 of 13 susceptible) of female rats and 56% (9 of 16 susceptible) of male rats (P > 0.05, male vs. female). beta-Adrenergic receptor blockade prevented sustained VT in females only [1 of 9 susceptible females (11%) vs. 6 of 9 susceptible males (67%), P < 0.05]. Ovariectomy did not significantly reduce the susceptibility to reperfusion arrhythmias [5 of 9 susceptible (56%)]. In sharp contrast, orchidectomy significantly increased the susceptibility to reperfusion arrhythmias [9 of 9 susceptible (100%)]. Finally, beta-adrenergic receptor blockade prevented sustained VT in ovariectomized females [0 of 4 susceptible (0%)] and orchidectomized males [0 of 7 susceptible (0%)], but the protective effect of beta-blockade was due to a reduction in heart rate in males only. Thus gonadal hormones influence the susceptibility to reperfusion-induced arrhythmias, as well as the effects and mechanisms of beta-adrenergic receptor blockade.
Lujan
Heidi L
HL
Department of Physiology, Wayne State University School of Medicine, Detroit, MI 48201, USA. hlujan@med.wayne.edu
Kramer
Victoria J
VJ
DiCarlo
Stephen E
SE
D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage*; D000818:Animals; D004198:Disease Susceptibility / Q000378:metabolism / Q000628:therapy; D005260:Female; D008297:Male; D015428:Myocardial Reperfusion Injury / Q000150:complications / Q000378:metabolism*; D010052:Ovariectomy; D051381:Rats; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D012737:Sex Factors; D017180:Tachycardia, Ventricular / Q000209:etiology / Q000378:metabolism*
D000319:Adrenergic beta-Antagonists; D011943:Receptors, Adrenergic, beta