RESUMO
The effect of nibentan (2.5 and 25 muM) on extrasystolic and post-extrasystolic contraction of isolated and perfused papillary muscle was studied. The muscle contracted in an isometric regimen at a rate of external electrical stimulation of 0.5 Hz in a temperature-stabilized chamber (36.0+0.5 degrees C). The extrasystolic contraction was induced with an extra electrical pulse applied 0.25 sec after the regular stimulus. Nibentan decreased the amplitude of extrasystolic contraction in a dose-dependent manner. At the same time, the effect of nibentan on extrasystolic contraction practically did not depend on its concentration. It is concluded that nibentan produces a dose-dependent effect on excitability of rat ventricular myocardium, and in parallel improves calcium-accumulating capacity of the sarcoplasmic reticulum in cardiomyocytes.
