title: Inhibition of cardiac phosphodiesterase III by the novel cardiotonic agent 6-[4-(4'-pyridyl)aminophenyl]-4,5-dihydro-3(2H)-pyridazinone hydrochloride.
abstract: The novel cardiotonic agent 6[4-(4'-pyridyl)aminophenyl]-4,5-dihydro-3(2H)-pyridazinone hydrochloride (MCI-154) was investigated for its cardiovascular effects and its mechanism of action. In the anaesthetized rat MCI-154 (0.01-0.3 mumol/kg i.v., bolus injection) produced a dose-dependent increase in left ventricular dP/dt, and a decrease in mean arterial pressure. A relatively small increase in heart rate was observed. The drug inhibited selectively canine cardiac phosphodiesterase III (IC50 2.5 +/- 0.6 mumol/l). In skinned porcine trabeculae, MCI-154 produced only a small increase in the Ca2+-sensitivity of the contractile proteins. The results suggest that MCI-154 is a potent cardiotonic agent, and that inhibition of phosphodiesterase III may be a important component of this effect.
authors.affiliation: Department of Pharmacology, Orion Pharmaceutica, Espoo, Finland.
authors.forename: L C
authors.initials: LC
authors.lastname: Sellin
authors.forename: A
authors.initials: A
authors.lastname: Alajoutsijärvi
authors.forename: K
authors.initials: K
authors.lastname: Törnquist
authors.forename: M
authors.initials: M
authors.lastname: Fraser
authors.forename: A
authors.initials: A
authors.lastname: Pippuri
authors.forename: I
authors.initials: I
authors.lastname: Ojala
mesh_terms: D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000037:antagonists & inhibitors; D000758:Anesthesia; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002118:Calcium / Q000494:pharmacology; D002316:Cardiotonic Agents / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006339:Heart Rate / Q000187:drug effects; D066298:In Vitro Techniques; D007275:Injections, Intravenous; D008297:Male; D009206:Myocardium / Q000201:enzymology*; D010726:Phosphodiesterase Inhibitors; D011724:Pyridazines / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D013552:Swine; D014129:Trabecular Meshwork / Q000201:enzymology
chemical_list: D002316:Cardiotonic Agents; D010726:Phosphodiesterase Inhibitors; D011724:Pyridazines; C052228:MCI 154; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D002118:Calcium