Smooth muscle cells of the guinea-pig portal vein were dispersed by enzymatic treatment and recordings of membrane currents were made in the whole-cell mode by the patch-clamp technique. The effects of extracellular application of cicletanine-hydrochloride on the whole-cell currents of isolated smooth muscle cells from the guinea-pig portal vein were studied in solutions containing a normal concentration of calcium (2.5 mM). 2. Cicletanine, 10 to 100 microM, reduced the voltage-dependent inward calcium current with an IC50 of 250 microM. These effects of cicletanine were reversible. 3. The action of cicletanine on calcium currents can be interpreted as a decrease of the availability of calcium channels but not by an alteration of the time course or voltage-dependency of inactivation. 4. The control calcium current was enhanced by application of Bay K 8644. On this enhanced inward current, cicletanine also exerted inhibitory effects which were not use-dependent. 5. Cicletanine, 1 to 100 microM, did not enhance outward potassium currents. 6. It is concluded that at least one component of the vasorelaxant effects of cicletanine is produced by inhibition of calcium currents.
摘要
采用酶解法分散豚鼠门静脉平滑肌细胞，并运用膜片钳技术在全细胞模式下记录膜电流。在含有正常钙浓度（2.5 mM）的溶液中，研究了细胞外应用盐酸西氯他宁对豚鼠门静脉分离的平滑肌细胞全细胞电流的影响。2. 10至100微摩尔的西氯他宁可降低电压依赖性内向钙电流，其半数抑制浓度（IC50）为250微摩尔。西氯他宁的这些作用是可逆的。3. 西氯他宁对钙电流的作用可解释为钙通道可利用性的降低，而非失活时间进程或电压依赖性的改变。4. 应用Bay K 8644可增强对照钙电流。在这种增强的内向电流上，西氯他宁也发挥了非使用依赖性的抑制作用。5. 1至100微摩尔的西氯他宁不会增强外向钾电流。6. 得出的结论是，西氯他宁血管舒张作用的至少一个成分是由抑制钙电流产生的。
