Effect of urapidil on L-type calcium current in rat ventricular myocytes / 中华麻醉学杂志

ABSTRACT

Objective To determine the effects of urapidil on L-type calcium current(I_(Ca-L))in rat cardiomyocytes.Methods Ventricular myocytes were isolated from SD rats of either sex(250-280g)by retrograde perfusion of the hearts via aorta with calcium-free Tyrode solution containing enzyme as described elsewhere.Rod shaped cells with clear borders and striations were selected.Eighteen cells were randomly divided into 3 groups(n =6 each)A urapidil group;B urapidil+methysergide group and C methysergide group.All the cells in the three groups were peffused first with Tyrode solution for 1 min(T_1).In group A and C cells were then peffused with Tyrode solution containing 0.4 ?mol?L~(-1) urapidil(A)or 40 nmol?L~(-1) methysergide(C)for 1 min(T_2) while in group B cells were perfused fwst with Tyrode solution containing 0.4 ?mol?L~(-1) urapidil for 1 min (T_2) then with Tyrode solution containing methysergide 40 nmol?L~(-1) for 1 min (T_3).Finally the cells were again perfused with regular Tyrode solution for 1 min(T_4)to wash out the drugs.The peak of I_(Ca-L) was recorded at T_(1-4) by means of the whole cell patch clamp technique with use of Axo patch 200B.Results In group A,B and C the peak of I_(ca-L) at T_2 was significantly lower than that at T_1 but there was no significant difference between the peak of I_(ca-L) at T_1 and T_4.In group B the peak of I_(Ca-L) at T_3 was significantly lower than that at T_2.Conclusion Urapidil inhibits L-type calcium current in rat isolated cardiomyoeytes.It's inhibitory effect may not be mediated by 5-H_(1A) receptor.