Aldosterone and testosterone. two steroid hormones structurally related but with opposite electrophysiological properties during myocardial ischemia-reperfusion.

Steroid hormones appear to be a key factor in the gender differences in the rates and severity of cardiovascular diseases. Aldosterone and testosterone have typical steroid ring structure but despite this, they demonstrate very different properties. During acute myocardial ischemia-reperfusion, the deleterious impact of aldosterone is now well established. Conversely, the electrophysiological impact of testosterone in this context remained unknown. We used female rabbit in vitro models and standard microelectrode technique including right ventricle mimicking the "border zone" existing between normal and ischemic/reperfused areas and isolated right ventricle experiments to assess the acute electrophysiological impact of both aldosterone and testosterone. During ischemia-reperfusion, acute superfusion of 10 and 100 nmol/L testosterone decreased normoxic and reperfused action potential duration at 90% (APD90 ), systematically induced conduction blocks and decreased APD90 dispersion between ischemic and non-ischemic areas (from 98±4 ms to 57±7 ms and 66±3 ms, for respectively testosterone 10 and 100 nmol/L, P<0.05). Testosterone 10 and 100 nmol/L concomitantly decreased sustained premature ventricular contractions (PVCs) occurrence (from 55% to 0%, P<0.05). Conversely, aldosterone 10 and 100 nmol/L increased normoxic and reperfused APD90 , APD90 dispersion and reperfusion-induced PVCs. Furthermore, testosterone demonstrated cycle length-dependent effects on APD90 for high heart rate, whereas aldosterone did not exhibit any significant effect compared with controls. During acute myocardial ischemia-reperfusion, acute superfusion of physiological concentrations of testosterone seemed to be antiarrhythmic by removing a pro-arrhythmic substrate (APD90 dispersion), inducing conduction blocks and decreasing triggered activities (PVCs occurrence). Further experiments are warranted to confirm our results. This article is protected by copyright. All rights reserved.