粉防己碱对离体狗隐静脉的收缩作用

Contractile Responses of Dog Saphenous Vein Induced by Tetrandrine

粉防己碱对狗隐静脉（ＤＳＶ）的去极化收缩有抑制作用。但在抑制后冲洗时却引起明显收缩。α２－肾上腺素能受体拮抗剂Ｒａｕｗｏｓｃｉｎｅ１０－７ｍｏｌ及ＫＣｌ４０ｍｍｏｌ／Ｌ能抑制冲洗波的出现；单独使用Ｔｅｔ也能诱发ＤＳＶ缓慢的张力增加，而ＫＣｌ２０ｍｍｏｌ／Ｌ既能加速Ｔｅｔ诱发收缩的出现也能增强α２－肾上腺素能受体激动剂Ｂ－ＨＴ９２０的缩血管效应。对ＢａｙＫ８６４４诱发的ＤＳＶ收缩。Ｔｅｔ既不能抑制也无冲洗波出现。提示在低Ｋ＋条件下Ｔｅｔ能激活α２－肾上腺素能受体而引起收缩，在高Ｋ＋存在时激活Ｎａ－ＫＡＴＰ酶导致去极化收缩的舒张。

etrandrine(Tet)has repeatedly been shown to cause vascular relaxation in arteries via inhibition of voltage-dependent Ca2+ channels.In this study,we stu- died the vasodilation of isolated dog saphenous vein(DSV)by Tet by examining its effect on elevated potassium-induced contraction.KCl-induced contraction was inhibited by 40uM Tet Following maximal rela- xation by Tet,DSV preparation contracted again upon washout of KCl by normal Krebs so lution.This wash-induced contraction in the presence of Tet was stu- did,with the following results:(1)The wash-induced contraction of DSV was unaffected by 10-6 M TTX, 10-6M ouabain,10-5M atropine and 10-6M indometha- cin.(2)A lmost comp lete inhibition of wash-induced contraction of DSV was observed when phentolamine 10-6M was added.(3)Furthermore,this wash-induced contraction could be inhibited by the a lpha-2-adrenoceptor antagonistrauwolscine 10-7M but not be the a lphal-1-adrenoceptor antagonist prazosin 10-7M.(4)The contractile responses of DSV may be induced by 40uM Tet alone in nor-mal Krebs solution.(5)The contractile responses of DSV induced by the a lpha-2-adrenoceptor agonist B-HT 920 was enhanced by lower concentration of KC (20mM).(6)Compared to the dog mesenteric veins(DMV),mesenteric arteries(DMA)and aortas(DAO),the wash-induced contraction were the largest in DSV, med-ium in DMV and not observed in DMA and DAO in good corre lation with thedensity of alpha-2-adrenoceptor in these vessels as studied by readio ligand bin-ding.These findings suggest that Tet may interact with the a lpha-2-adrenoceptorcausing vascular constriction which is enhanced upon preexposure to KCl.