Blood pH and the actions of nifedipine on cardiac excitation-contraction coupling.
Hearts from male Sprague-Dawley rats were perfused, by the Lagendorff method, with calcium-free Krebs solution (containing either adrenaline or a high level of potassium) at pH 7.48 (control), 7.26 (acidosis) or 7.69 (alkalosis). When the hearts stopped contracting, a dose of nifedipine or its vehicle was given before measuring the force of contraction, coronary perfusion pressure and heart rate in response to graded doses of calcium. The calcium-antagonising efficacy of nifedipine was reduced during acidosis in both adrenaline- and potassium-stimulated hearts, but the reduction was greater in the adrenaline-stimulated hearts. Alkalosis led to a small increase in the efficacy of nifedipine on adrenaline- and potassium-stimulated contractions.
Achike
F I
FI
Department of Pharmacology, Faculty of Medicine, University of Hong Kong.
Dai
S
S
Ogle
C W
CW
D000818:Animals; D004837:Epinephrine / Q000494:pharmacology; D006439:Hemodynamics; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D009543:Nifedipine / Q000494:pharmacology*; D010477:Perfusion; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley
D009543:Nifedipine; D011188:Potassium; D004837:Epinephrine