Calcium agonism, a new mechanism for positive inotropy. Hemodynamic effects and mode of action of BAY K 8644.
BAY K 8644 [methyl 1,4-dihydro-2,6-dimethyl-3-nitro-4-(2-trifluoromethyl -phenyl)-pyridine-5-carboxylate] is a nifedipine-like 1,4-dihydropyridine (DHP). In contrast to the well-known calcium antagonistic DHPs, it has vasoconstricting and positive inotropic properties. In the pentobarbital-anesthetized dog, it increases blood pressure, peripheral resistance, and left ventricular (dP/dt)max dose-dependently from 3 to 100 micrograms/kg i.v. If the vagus is blocked, heart rate is unchanged. In the isolated isovolumic perfused guinea pig heart, BAY K 8644 has positive inotropic and coronary constricting actions from 10(-9) mole/liter. At 10 times higher concentrations, this compound also increases the heart rate up to 20%. BAY K 8644 has no effect on rabbit aortic strip at physiological K+ concentrations, but potentiates the K+ -induced contraction of the strip. In the partially depolarized aortic strip (18 mM K+), BAY K 8644 induces concentration-dependent contractions, which are competitively inhibited by the calcium-antagonistic DHP nifedipine. Chemically different calcium antagonists such as verapamil or diltiazem inhibit the BAY-K-8644-induced contractions noncompetitively. These results indicate that a specific DHP receptor exists, which binds nifedipine and BAY K 8644. In contrast to the calcium-antagonistic DHPs like nifedipine, BAY K 8644 increases the calcium influx into the cell.
Schramm
M
M
Towart
R
R
Kazda
S
S
Thomas
G
G
Franckowiak
G
G
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D002302:Cardiac Output / Q000187:drug effects; D003326:Coronary Circulation / Q000187:drug effects; D046508:Culture Techniques; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D005260:Female; D006168:Guinea Pigs; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects*; D007473:Ion Channels / Q000187:drug effects; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D009200:Myocardial Contraction / Q000187:drug effects*; D009206:Myocardium / Q000378:metabolism; D009543:Nifedipine / Q000031:analogs & derivatives* / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011817:Rabbits; D014655:Vascular Resistance / Q000187:drug effects
D007473:Ion Channels; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D009543:Nifedipine; D011188:Potassium; D002118:Calcium