title: Effects of a cardiotonic quinolinone derivative Y-20487 on the isoproterenol-induced positive inotropic action and cyclic AMP accumulation in rat ventricular myocardium: comparison with rolipram, Ro 20-1724, milrinone, and isobutylmethylxanthine.
abstract: The effect of a new cardiotonic agent Y-20487 [6-(3,6-dihydro-2-oxo-2H-1,3,4-thiadiazin-5-yl)-3,4-dihydro-2(1H)- quinolinone] on cyclic AMP levels of rat ventricular cardiomyocytes and the contractile force of papillary muscles was investigated in comparison with selective cyclic AMP phosphodiesterase (PDE) inhibitors, milrinone (PDE-III selective), rolipram and Ro 20-1724 (PDE-IV selective), and a nonselective inhibitor 3-isobutyl-1-methylxanthine (IBMX). Rolipram and Ro 20-1724 did not elicit cyclic AMP accumulation and positive inotropy, but they potentiated the isoproterenol (ISO)-induced cyclic AMP accumulation more effectively than IBMX. Rolipram was more effective than Ro 20-1724 in enhancing ISO-induced cyclic AMP accumulation but was less effective in enhancing the ISO-induced positive inotropic effect, indicating that these agents produce a differential action on cyclic AMP metabolism and inotropy. Milrinone and Y-20487 elicited cyclic AMP accumulation and positive inotropy by themselves. Whereas milrinone scarcely affected the ISO-induced effects, Y-20487 shifted the concentration-response curve for the positive inotropic effect of ISO to the left to the same extent that IBMX did. Y-20487, however, was much less effective than IBMX in enhancing the ISO-induced cyclic AMP accumulation. The present results indicate that in rat ventricular myocardium, PDE-IV may play a crucial role in breakdown of cyclic AMP generated by beta-adrenoceptor stimulation, whereas other types of PDE isoenzymes, including PDE-III, may be responsible for the cyclic AMP accumulation and direct positive inotropic effect induced by PDE inhibitors.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D012368:4-(3-Butoxy-4-methoxybenzyl)-2-imidazolidinone / Q000494:pharmacology; D000818:Animals; D002316:Cardiotonic Agents / Q000494:pharmacology*; D000242:Cyclic AMP / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D006339:Heart Rate / Q000187:drug effects; D007545:Isoproterenol / Q000494:pharmacology*; D008297:Male; D020105:Milrinone; D009200:Myocardial Contraction / Q000187:drug effects*; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D010210:Papillary Muscles / Q000187:drug effects; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D011728:Pyridones / Q000494:pharmacology; D011760:Pyrrolidinones / Q000494:pharmacology; D015363:Quinolones / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D020889:Rolipram; D013268:Stimulation, Chemical; D013829:Thiadiazines / Q000494:pharmacology*
chemical_list: D002316:Cardiotonic Agents; D010726:Phosphodiesterase Inhibitors; D011728:Pyridones; D011760:Pyrrolidinones; D015363:Quinolones; D013829:Thiadiazines; C078451:6-(3,6-dihydro-2-oxo-2H-1,3,4-thiadiazin-5-yl)-3,4-dihydro-2(1H)-quinolinone; D012368:4-(3-Butoxy-4-methoxybenzyl)-2-imidazolidinone; D000242:Cyclic AMP; D020105:Milrinone; D020889:Rolipram; D007545:Isoproterenol; D015056:1-Methyl-3-isobutylxanthine