Zhao Xue Ling, Gu Dong Fang, Qi Zhi Ping, Chen Ming Hong, Wei Ting, Li Bao Xin, Yang Bao Feng
Department of Pharmacology, Harbin Medical University, Harbin, China.
Eur J Pharmacol. 2009 Apr 1;607(1-3):15-22. doi: 10.1016/j.ejphar.2009.02.013. Epub 2009 Feb 27.
Human ether-à-go-go-related gene (hERG) has an important role in the repolarization of the cardiac action potential. Sophocarpine and sophoridine are quinolizidine alkaloids and their structures are similar. Our aim was to investigate the effects of sophocarpine or sophoridine on hERG-encoded K(+) channels and the underlying structure-activity relationships. The effects of sophocarpine and sophoridine were examined on stably expressed hERG channels in HEK293 cells using a whole-cell patch clamp technique and Western blot analysis. The oil-water partition coefficients of sophocarpine and sophoridine were determined by a validated RP-HPLC method. At 300 microM, fractional block was 60.9+/-1.4% for sophocarpine versus 41.9+/-2.0% for sophoridine. Compared with sophocarpine, voltage-dependence of hERG channels inhibition by sophoridine was more notable. Sophoridine altered the activation properties, but not sophocarpine. Sophocarpine shifted the inactivation curve in a negative direction, but not sophoridine. Both drugs had no significant effect on the expression of hERG protein. The partition coefficients for the n-octanol/water system of sophocarpine and sophoridine at 37 degrees C were 16.03+/-0.42 and 1.94+/-0.03, respectively. In summary, sophocarpine and sophoridine are low potency blockers of hERG channels that functions by changing the channel kinetics, and sophocarpine is a more potent blocker of hERG K(+) channels than sophoridine, which may be due to higher hydrophobic nature of sophocarpine compared with sophoridine. Sophocarpine may have a higher binding affinity for the inactivate state. In contrast, sophoridine has a higher binding affinity for the open state. Both drugs have no effect on the generation and trafficking of hERG protein.
人醚 - 去极化相关基因（hERG）在心脏动作电位的复极化过程中起重要作用。槐果碱和槐定碱是喹诺里西啶生物碱，它们的结构相似。我们的目的是研究槐果碱或槐定碱对hERG编码的钾通道的影响以及潜在的构效关系。采用全细胞膜片钳技术和蛋白质印迹分析，检测了槐果碱和槐定碱对HEK293细胞中稳定表达的hERG通道的影响。通过验证的反相高效液相色谱法测定了槐果碱和槐定碱的油水分配系数。在300微摩尔浓度下，槐果碱的阻断率为60.9±1.4%，而槐定碱为41.9±2.0%。与槐果碱相比，槐定碱对hERG通道抑制的电压依赖性更显著。槐定碱改变了激活特性，而槐果碱没有。槐果碱使失活曲线向负向移动，而槐定碱没有。两种药物对hERG蛋白的表达均无显著影响。在37℃时，槐果碱和槐定碱在正辛醇/水体系中的分配系数分别为16.03±0.42和1.94±0.03。总之，槐果碱和槐定碱是hERG通道的低效阻断剂，通过改变通道动力学发挥作用，且槐果碱是比槐定碱更有效的hERG钾通道阻断剂，这可能是由于槐果碱比槐定碱具有更高的疏水性。槐果碱对失活状态可能具有更高的结合亲和力。相比之下，槐定碱对开放状态具有更高的结合亲和力。两种药物对hERG蛋白的产生和转运均无影响。
