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

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We investigated the direct action of angiotensin II (Ang II) on myocardial conduction and transmembrane action potential immediately after reoxygenation.Method: After 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.Results: In 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).Conclusion: RES-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.