Direct action of angiotensin II on the conduction through papillary muscle preparations of rat heart immediately after reoxygenation

We investigated the direct action of angiotensin II (Ang II) on myocardial conduction and transmembrane action potential immediately after reoxygenation.MethodAfter superfusion in a simulated ischemic solution, ventricular papillary muscle preparations of rat heart were washed with oxygenated Tyrode solution containing Ang II, Ang II plus CV-11974 (an AT1 receptor blocker), or Ang II plus 5-hydroxydecanoic acid (mito-KATP blocker), under rapid electrical stimulation (RES) for 60 s.ResultsIn the control experiments, the incidence of conduction delay and block was the highest within the first 10 s, and subsequently, 1:1 conduction was established after 40 s. Ang II significantly enhanced the 2:1 conduction block during the later phase of RES (40–60 s after reoxygenation). This effect of Ang II was abolished by either CV-11974 (P<0.001) or 5-HD (P<0.001).ConclusionRES-induced conduction delay and block immediately after reoxygenation were accelerated by Ang II, which could be relevant to the maintenance of reperfusion arrhythmias. The mito-KATP channel may participate in the mechanism underlying this phenomenon.