Activation of the Langendorff perfused rat heart depolarized by increased external potassium concentration.
Myocardial activation under depolarized conditions was studied in spontaneously beating Langendorff perfused hearts from albino rats. Depolarization was obtained by increasing external potassium concentration in steps (5.4, 7.4, 10, 10.5, 11 and 11.5 mM) in the perfusing solution with or without adrenaline (Adr). Left ventricle isovolumic systolic pressure and coronary flow did not change as external potassium increased, albeit being larger with Adr in the perfusing solution. Atrial and ventricular rates decreased, the latter showing a larger decline. The same behaviour was displayed by perfused hearts, with higher rates being developed by the group with Adr. PR interval and QRS complex duration increased as a function of external potassium. PR intervals were the same in both groups but QRS duration was larger in the Adr group, indicating that AV conduction was not changed in presence of Adr but intraventricular conduction was delayed in that situation. It was also observed that in the great majority of perfused hearts, differing from isolated preparations, ventricular mechanical activity ceased at around 11.5 mM external potassium.
Abaurre
P F
PF
Departamento de Ciencias Fisiológicas, Centro Biomédico, Universidade Federal do Espírito Santo, Vitoria ES, Brasil.
Stefanon
I
I
Mill
J G
JG
Vassallo
D V
DV
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D016275:Atrial Function; D001794:Blood Pressure / Q000187:drug effects; D004562:Electrocardiography / Q000187:drug effects; D004837:Epinephrine / Q000494:pharmacology*; D005260:Female; D006321:Heart / Q000187:drug effects / Q000502:physiology*; D006325:Heart Atria / Q000187:drug effects; D006329:Heart Conduction System / Q000187:drug effects* / Q000502:physiology; D006339:Heart Rate / Q000187:drug effects; D006352:Heart Ventricles / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D010477:Perfusion; D011188:Potassium / Q000494:pharmacology*; D051381:Rats; D016276:Ventricular Function
D011188:Potassium; D004837:Epinephrine