Blocking effects of phentolamine on L-type calcium current and ATP-sensitive potassium current in guinea pig ventricular myocytes

目的：研究酚妥拉明对豚鼠心室肌细胞Ｌ型钙电流及ＡＴＰ敏感钾电流的作用．方法：用膜片钳的全细胞记录方式观察钙电流和ＡＴＰ敏感钾电流．结果：酚妥拉明５，２５和１００μｍｏｌ·Ｌ－１对钙电流呈浓度依赖性和非电压依赖性的抑制作用，抑制率分别为１７％，２３％和３０％，而对电流电压关系没有影响．这一抑制作用与酚妥拉明对α１和α２受体的作用无关．酚妥拉明１００μｍｏｌ·Ｌ－１可显著抑制ＤＮＰ诱导产生的ＡＴＰ敏感钾电流，抑制率为７５％．结论：酚妥拉明显著抑制豚鼠心室肌细胞Ｌ型钙电流和ＡＴＰ敏感钾电流．

AIM: To study the effect of phentolamine on L type calcium currents ( I Ca ) and ATP sensitive K^+ currents ( I K,ATP ) in ventricular myocytes. METHODS: I Ca and I K,ATP were observed using patch clamp techniques in whole cell recording configuration. RESULTS: Phentolamine reduced I Ca of ventricular myocytes in concentration dependent and voltage independent manners. Phentolamine 5, 25, and 100 μmol·L -1 decreased I Ca from 370±99 nA to 310±95 nA (17 % block, n =6, P <0 01), from 230±98 nA to 180±73 nA (23 % block, n =5, P <0 05), and from 293±66 nA to 206±44 nA (30 % block, n =5, P <0 01), respectively, without affecting the current voltage relationship. Prazosin 100 μmol·L -1 and yohimbine 100 μmol·L -1 , which were specific blockers of α 1 and α 2 adrenoceptors respectively, did not show the inhibitory effect on I Ca . Phentolamine 100 μmol·L -1 also inhibited the I K,ATP induced by 2,4 dinitrophenol (DNP) at 0 mV from 3 2±0 6 nA to 0 8±0 5 nA (75 % block, n =4, P <0 01). CONCLUSION: Phentolamine directly inhibits I Ca and I K,ATP in guinea pig ventricular myocytes.