RESUMEN
AIM To study the effects of A 3 site (components), extracted from Angelica naphtha (total oil),on physiological properties of isolated rat atrium and action potential of isolated guinea pig ventricular papillary muscles. METHODS Spontaneous beats, contractile force and functional refractory period(FRP) of isolated atrial muscle were recorded according to the regular methods. Standard microelectrode intracellular recording technique was used to record action potential(AP) of ventricular papillary muscles. RESULTS A 3 site(10～160 mg?L -1 ) dramatically inhibited spontaneous beats of isolated rat right atrium and made beats stop with 160 mg?L -1 . A 3 site concentration dependently reduced contractile force of isolated rat left atrium induced by electrostimulating, with the IC 50 value of 52 3 mg?L -1 . A 3 site(40～100 mg?L -1 ) obviously prolonged FRP. The FRP was prolonged from 106 ms (as control) to 130 ms at final concentration of 100 mg?L -1 . A 3 site decreased action potential amplitude (APA), shortened 20%APD(APD 20 ) and 90%APD(APD 90 ), but had no significant effect on RP of AP. CONCLUSION The mechanism of these effects of A 3 site on myocardial physiological properties and action potential was probably associated with blocking the influx of Ca 2+ and Na +, promoting K + outflux.