Höcht Christian, Di Verniero Carla, Opezzo Javier A W, Taira Carlos A
Department of Pharmacology, Faculty of Pharmacy and Biochemistry, University of Buenos Aires, Junín 956, (C1113AAD)Buenos Aires, Argentina.
Pharmacol Res. 2003 Mar;47(3):181-8. doi: 10.1016/s1043-6618(02)00334-1.
The chronotropic effects of metoprolol (MP) in vivo after intravenous administration and in vitro in isolated atria of aortic coarctated rats were studied. MP levels in arterial dialysates and changes in arterial pressure and heart rate (HR) were determined after intravenous administration of MP. Affinity of MP by means of shifting of noradrenaline concentration-response curve and the inverse agonist activity of MP were studied in isolated atria. The IC(50) value of MP cardiac effect was smaller in aortic coarctated rats (13.0+/-5.4 ng ml(-1), n=5) than in sham operated (SO) rats (36.2+/-4.6 ng ml(-1), n=5). In isolated atria, no difference was found in MP dissociation constant and its inverse agonist activity between both experimental groups. In conclusion, the affinity and inverse agonism activity of MP would not be altered in aortic coarctated rats. A greater sensibility to the chronotropic effect of MP was found in coarctated rats.
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