Negative chronotropic effect of endothelin-1 (ET-1) in the cardiac pacemaker tissue.
The aim of this study was to asses the direct effect of ET-1 on spontaneous discharge rate of the pacemaker tissue in the presence of isoproterenol. The experiments were performed on pacemaker tissue of the isolated right auricle of the right heart atrium of a two-day-old rat. The spontaneous discharge rate of the pacemaker tissue was recorded on the ECG apparatus and analyzed by the computer. ET-1 alone did not significantly affect the discharge rate of the pacemaker tissue. Isoproterenol rapidly increased the discharge rate of the pacemaker tissue. ET-1 had negative chronotropic effect in the presence of isoproterenol. JKC-301, a blocker of ET(A) receptors, significantly reduced the negative chronotropic effect of ET-1 in the presence of isoproterenol, whereas IRL-1038, a blocker of ET(B) receptors, did not significantly affect the negative chronotropic effect of ET-1 in the presence of isoproterenol. In conlusion, the negative chronotropic effect of ET-1 in the presence of beta-adrenergic stimulation the pacemaker tissue of the right auricle of the right heart atrium of the two-day-old rat is mediated by ET(A) receptors.
Goraca
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Department of Experimental and Clinical Physiology, Institute of Physiology and Biochemistry, Medical University of Lodz, Poland. agoraca@zdn.am.lodz.pl
D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology; D002316:Cardiotonic Agents / Q000494:pharmacology; D003864:Depression, Chemical; D004562:Electrocardiography; D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1 / Q000494:pharmacology*; D006325:Heart Atria / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects* / Q000502:physiology; D007545:Isoproterenol / Q000494:pharmacology; D009842:Oligopeptides; D011224:Prazosin / Q000494:pharmacology; D051381:Rats
D000959:Antihypertensive Agents; D002316:Cardiotonic Agents; D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1; C096173:JKC 301; D009842:Oligopeptides; D007545:Isoproterenol; D011224:Prazosin