Both the prolongation APD and occurence of EADs evoked by ET 1 were abolished by either BQ 123,an ET A receptor selective antagonist,or Nif,a Ca 2+ channel blocker.

• ETA 受体拮抗剂BQ 12 3和Ca2 + 通道阻断剂硝苯吡啶可消除ET 1的上述作用。