尼群地平和非洛地平对豚鼠心肌细胞钙通道的双相作用

DUAL ACTION OF NITRENDIPINE AND FELODIPINE ON THE MYOCARDIAL CALCIUM CHANNEL OF GUINEA PIG

研究尼群地平（ｎｉｔｒｅｎｄｉｐｉｎｅ，Ｎｉｔ）、非洛地平（ｆｅｌｏｄｉｐｉｎｅ，Ｆｅｌ）对豚鼠乳头肌的电生理作用。用细胞内微电极技术测定药物的作用。结果：低浓度的Ｎｉｔ１和１０ｎｍｏｌ·Ｌ－１，延长快反应动作电位的二相坪台期（ＡＰＤ）中的ＡＰＤ２０、ＡＰＤ５０、ＡＰＤ９５和有效不应期（ＥＲＰ），其作用可被冲洗掉。高浓度的Ｎｉｔ０．３和１μｍｏｌ·Ｌ－１可浓度依赖性缩短异丙肾上腺素诱发的慢反应动作电位的时程ＡＰＤ５０和ＡＰＤ９０。其作用可被冲洗掉，但Ｎｉｔ的浓度增加到５和１０μｍｏｌ·Ｌ－１时，Ｎｉｔ对慢反应动作电位时程的作用，就不能冲洗掉。Ｆｅｌ也有相似作用。Ｎｉｔ和Ｆｅｌ对动作电位时程具有高浓度缩短，低浓度延长的的双相作用。硝苯啶（ｎｉｆｅｄｉｐｉｎｅ，Ｎｉｆ）１ｎｍｏｌ·Ｌ－１可明显延长动作电位时程，但维拉帕米（ｖｅｒａｐａｍｉｌ．Ｖｅｒ）０．１，１和５ｎｍｏｌ·Ｌ－１对动作电位无明显作用。结论：Ｎｉｔ，Ｆｅｌ在远低于阻断心肌钙通道的浓度时对心肌钙通道具有激动作用，但不是所有钙拮抗剂都具有类似作用。

PURPOSE To investigate the dual action of nitrendipine (Nit)and felodipine (Fel)on the myocardial calcium channel of guinea-pig.METHODS Effects of Nit and Fel on action potentials of guinea pig papillary muscles were studied by intracelluar microelectrodes.RESULTS Nit 0.33 and 1μmol·L-1 markedly shortened the APD90 and APD90 of slow AP elicited by isoprenaline. At 5 and 10μmol·L-1,the effect of Nit was not reversible on washout,but at 1 and 3μmol·L-1,it was.In the fast AP experiment,Nit 1 and 10 nmol·L-1 prolonged the APD50, APD20, APD50, APD50 and ERP.Fel had similar effects of Nit on action potentials (APs) of guinea pig papillary muscles.(Nif.0.1 nmol·L-1 had no effec effect on Aps of papillary muscle of guinea pig.But at 1 nmol·L-1, it prolonged APD30, APD50 and APD90 respectively.Verapamil 0.1 and 5 nmol·L-1 all had no effects on APD.CONCLUSIONS Nit,Fel and Nif at much lower concentrations than those of blocking Ca2+ channel probably had an agonistic effect on the channel.