Influence of dihydropyridine-type calcium agonists on hemodynamics and myocardial ischemia in isolated rabbit hearts.
Calcium (Ca) agonists like Bay k 8644 ((-)-S-1,4-dihydro-2,6-dimethyl-3-nitro-4-(2-trifluoromethylphenyl) pyridine-5-carboxylate (CAS 93468-89-4), may represent a new principle in the treatment of heart failure. Because of marked vasoconstrictive properties, these agents may have a deleterious effect on myocardial ischemia (MI). It was however demonstrated that contractility enhancement and coronary flow (CF) reduction do not automatically enlarge MI. Therefore, we investigated the influence of Bay k 8644 (10(-8) mol/l) in comparison to ouabain (1.5 x 10(-7) mol/l) in non-arrhythmogenic concentrations on MI in electrically paced isolated rabbit hearts (Langendorff, constant pressure: 70 cm H2O, Tyrode solution, Ca2+ 1.8 mmol/l, 180 beats/min). MI was induced by coronary artery ligation and quantified by epicardial NADH-fluorescence. Left ventricular pressure (LVP) was significantly increased by ouabain (+10-20%) but slightly diminished by Bay k 8644 (-10%) (p < 0.05). CF reduction after Bay k 8644 (-30%) was more pronounced than after ouabain (-10%) (p < 0.05), but both substances did reduce relative CF (CF/LVP x heart rate) to the same extent (-20-30%) (p > 0.05). Nevertheless, ouabain did not significantly influence epicardial NADH-fluorescence area or intensity (p > 0.05), whereas MI was significantly enlarged by Bay k 8644 (+30%) (p < 0.05). It is concluded that in isolated rabbit hearts ouabain and Bay k 8644 might influence CF-distribution differently with a more pronounced diminuation of the nutritive CF induced by Bay k 8644.
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AF
Institut für Pharmakologie, Universität Köln, Fed. Rep. of Germany.
Rösen
R
R
Sigmund
B
B
Fuchs
J
J
Ratke
R
R
Klaus
W
W
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000818:Animals; D002120:Calcium Channel Agonists / Q000494:pharmacology*; D003326:Coronary Circulation / Q000187:drug effects; D004095:Dihydropyridines / Q000494:pharmacology*; D005453:Fluorescence; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects*; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D017202:Myocardial Ischemia / Q000503:physiopathology*; D009243:NAD / Q000378:metabolism; D010042:Ouabain / Q000494:pharmacology; D011817:Rabbits; D016277:Ventricular Function, Left / Q000187:drug effects
D002120:Calcium Channel Agonists; D004095:Dihydropyridines; D009243:NAD; D010042:Ouabain; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester