The role of aging on ouabain- and epinine-induced ventricular arrhythmias in isolated rat heart

The contractile response to ouabain and beta-adrenoceptor agonists is reduced in the senescent as compared with the adult myocardium while the development of ventricular arrhythmias is increased. In the present study, we tested the electrical and mechanical response of hearts from 3-24 month old rats receiving 15 min. infusion of ouabain (6 x 10^-5 M), 5 min. of epinine (1.5 x 10^-7 M) and both simultaneously. The results obtained show that aging influences negatively both positive inotropic and arrhythmogenic ouabain and epinine effects although these phenomena are more pronounced after ouabain. However, when administered simultaneously, epinine doesn't modify arrhythmogenic effect of ouabain but reduces some its hemodynamic deleterious effect.