The effects of oleuropeoside were studied on the electromechanical properties of isolated
guinea-pig atria. In spontaneously beating right atria, oleuropeoside decreased the
amplitude of contractions (IC50 = 1.3 ± 0.2 × 10-4M), slightly decreased atrial rate, and lengthened sinus node recovery time. Oleuropeoside
also inhibited peak contractile force in electrically driven left atria incubated
in normal (IC50 = 1.5 ± 0.5 × 10-4M) and in 27mM K+ Tyrode solution (IC50 = 1.7 ± 0.4 × 10-4M). These negative inotropic effects were not accompanied by significant changes in
the characteristics of action potentials recorded in atria incubated in either normal
or depolarizing solutions. These results indicate that oleuropeoside produced an electromechanical
uncoupling that cannot be attributed to an inhibitory effect on Ca2+ entry through L-type channels. Therefore, the negative inotropic effect may reflect
an action of oleuropeoside perhaps at an intracellular level.
Oleuropeoside - guinea-pig atria - contraction - action potential -
Olea europaea
