en Inotropic and Chronotropic Effects of 6-Hydroxy-4- Methylquinolin-2(1H)-One Derivatives in Isolated Rat Atria Related Fields Related Fields مقاله کامل Full Length/Original Article Background: Selective phosphodiesterase (PDE3) inhibitors improve cardiac contractility and may use in congestive heart failure. However, their proarrhythmic potential is the most important side effect. Methods: In this research, we evaluated the potential cardiotonic activity of six new synthesized selective PDE3 inhibitors (6-hydroxy-4-methylquinolin-2(1H)-one derivatives) using the spontaneously beating atria model. In each experiment, atrium of reserpine-treated rat was isolated and the contractile and chronotropic effects of a synthesized compound were assessed. The 3-isobutyl-1-methylxanthine, a non-selective PDE inhibitor, was used for comparison. Results: The results showed that, among new compounds, the best pharmacological profile was obtained with the compound 6-[4-(4-methylpiperazine-1-yl)-4-oxobutoxy]-4-methylquinolin-2(1H)-one, C6, which displayed selectivity for increasing the force of contraction (168 &plusmn; 5% change over the control) rather than the frequency rate (138 &plusmn; 5% change over the control) at 300 &mu;M. However, C6 at concentrations of 10 and 100 &mu;M produced left and upward shift in the positive inotropic concentration-response curve of isoprenaline. The -log EC50 of isoprenaline was 8.843 &plusmn; 0.171 in the absence, 9.448 &plusmn; 0.138 and 9.456 &plusmn; 0.107 in the presence of 10, 100 &mu;M of C6, respectively (P<0.001, n = 6). Also, amrinone, a selective PDE3 inhibitor, shifted the isoprenaline concentration-response curve to the left and upward. The concentration of 10 and 100 &mu;M amrinone decreased -log EC50 of isoprenaline to 9.527 &plusmn; 0.287 and 9.423 &plusmn; 0.243, respectively (P<0.001, n = 6). Moreover, the positive chronotropic effect of isoprenaline was not affected by amrinone or C6. Conclusion: This study provides functional evidence for the positive inotropic effect of C6. Considering the augmentation of isoprenaline positive inotropic concentration-response with C6 and amrinone, we conclude that C6 produces its effect via potentiation of cAMP-dependent signaling system and possibly by inhibition of PDE3 activity. Phosphodiesterase inhibitor, 4-methylquinolinone derivatives, Inotropic activity, Rat atria, Isoprenaline 77 84 http://ibj.pasteur.ac.ir/browse.php?a_code=A-10-1-63&slc_lang=en&sid=1 Seyed Mohammad-Taghi Mansouri سید محمد تقی منصوری No Reza Shafiee-Nick رضا شفیعی نیک shafieer@mums.ac.ir Yes Heydar Parsaee حیدر پارسایی No Seyed Mohammad Seyedi سید محمد سیدی No Mohammad-Reza Saberi محمدرضا صابری No Hamid Sadeghian حمید صادقیان No