Nitric oxide-dependent modulation of the delayed rectifier K+ current and the L-type Ca2+ current by ginsenoside Re, an ingredient of Panax ginseng, in guinea-pig cardiomyocytes
Nitric oxide-dependent modulation of the delayed rectifier K+ current and the L-type Ca2+ current by ginsenoside Re, an ingredient of Panax ginseng, in guinea-pig cardiomyocytes
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DOI：
10.1038/sj.bjp.0705814
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发表时间：
2004-06-01
影响因子：
7.3
通讯作者：
Furukawa, T
中科院分区：
文献类型：
--
作者：
Bai, CX;Takahashi, K;Furukawa, T
1 人参皂苷 Re 是人参的主要成分，通过缩短动作电位持续时间 (APD) 从而防止过量 Ca2+ 流入，保护心脏免受缺血再灌注损伤。人参皂苷 Re 增强延迟整流 K+ 电流 (I-Ks,) 的缓慢激活成分并抑制 L 型 Ca2+ 电流 (I-Ca,I-I.)，这可能是 APD 缩短的原因。2 我们使用膜片钳技术的穿孔配置来确定人参皂苷 Re 在豚鼠心室肌细胞中增强 I-Ks 和抑制 I-Ca,I-L 的机制。3 S-甲基异硫脲 (SMT，1 mm) 是一氧化氮 (NO) 合酶 (NOS) 的抑制剂，而 N-乙酰基-L-半胱氨酸 (LNAC，1 mm) 是一种 NO 清除剂，可抑制 I-K 增强。应用NO供体硝普钠（SNP，1 mm），增强I-Ks的幅度与最大剂量（20μm）人参皂苷Re相似，随后应用人参皂苷Re未能增强I-Ks。相反，人参皂苷 Re (20 mum) 增强 I-Ks 后，随后应用的 SNP 未能进一步增强 I-Ks。 4 鸟苷酸环化酶抑制剂 1H-[1,2,4]恶二唑并[4,3-a]喹喔啉-1-one (ODQ，10 mum) 几乎抑制 I-Ks 增强，而硫醇烷基化试剂 N-乙基马来酰亚胺（NEM，0.5 毫米）。明显压制了它。还原剂二硫苏糖醇（DTT，5 mm）可逆转人参皂苷 Re 和 SNP 诱导的 I-Ks 增强。5 SMT (1 mum) 或 LNAC (1 mm) 消除了人参皂苷 Re (3 mum) 引起的 I-Ca.L 抑制。 NEM (0.5 mm) 不会抑制 I-Ca,I-L 抑制，DTT (5 mm) 不会逆转 I-Ca,I-L 抑制，而在 ODQ (10 mum) 存在的情况下，人参皂苷 Re (3 mum) 未能抑制 I-C,I-La。6 这些结果表明，人参皂苷 Re 诱导的 I-Ks 增强和 I-Ca,I-L 抑制涉及 NO 作用。通道蛋白的直接 S-亚硝基化似乎是 I-K 增强的主要机制，而 cGMP 依赖性途径则负责 I-Ca、I-L 抑制。
1 Ginsenoside Re, a major ingredient of Panax ginseng, protects the heart against ischemia-reperfusion injury by shortening action potential duration (APD) and thereby prohibiting influx of excessive Ca2+. Ginsenoside Re enhances the slowly activating component of the delayed rectifier K+ current (I-Ks,) and suppresses the L-type Ca2+ current (I-Ca,I-I.), which may account for APD shortening.2 We used perforated configuration of patch-clamp technique to define the mechanism of enhancement of I-Ks and suppression of I-Ca,I-L by ginsenoside Re in guinea-pig ventricular myocytes.3 S-Methylisothiourea (SMT, 1 mum), an inhibitor of nitric oxide (NO) synthase (NOS), and N-acetyl-L-cystein (LNAC, 1 mm), an NO scavenger, inhibited I-Ks enhancement. Application of an NO donor, sodium nitroprusside (SNP, 1 mm), enhanced I-Ks with a magnitude similar to that by a maximum dose (20 mum) of ginseonside Re, and subsequent application of ginsenoside Re failed to enhance I-Ks. Conversely, after I-Ks had been enhanced by ginsenoside Re (20 mum), subsequently applied SNP failed to further enhance I-Ks.4 An inhibitor of guanylate cyclase, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 10 mum), barely suppressed I-Ks enhancement, while a thiol-alkylating reagent, N-ethylmaleimide (NEM, 0.5 mm). clearly suppressed it. A reducing reagent, di-thiothreitol (DTT, 5 mm), reversed both ginsenoside Re- and SNP-induced I-Ks enhancement.5 I-Ca.L suppression by ginsenoside Re (3 mum) was abolished by SMT (1 mum) or LNAC (1 mm). NEM (0.5 mm) did not suppress I-Ca,I-L inhibition and DTT (5 mm) did not reverse I-Ca,I-L inhibition, whereas in the presence of ODQ (10 mum), ginsenoside Re (3 mum) failed to suppress I-C,I-La.6 These results indicate that ginsenoside Re-induced I-Ks enhancement and I-Ca,I-L suppression involve NO actions. Direct S-nitrosylation of channel protein appears to be the main mechanism for I-Ks enhancement, while a cGMP-dependent pathway is responsible for I-Ca,I-L inhibition.