Effects of 3,4-dihydroxyacetophenone in shortening of action potential duration of cardiac cells

The effects of 3,4-dihydroxy-acetophenone (DHAP) extracted from Ilex pubescens Hook. Et Arn. Var. glaber Chang, on the electrical activity of isolated ventricular septum of guinea pig heart were studied by means of intracellular record with glass capillary microelectrode. DHAP 0.5-1 mg/ml depressed markedly or even abolished phase 2, accelerated the repolarization course and greatly shortened the duration of action potential (APD). It increased the ratio of effective refractory period (ERP) to APD and inhibited the spontaneous activity of the cardiac cells. It had little effect on the rhythmic activity induced by aconitine. DHAP attenuated the contractile force of papillary muscle. All these effects, however, were reversible. It is supposed that DHAP may partially block the slow inward current (Isi) and delay the inactivation of fast ourward K+ current.