FATTY ACID MODULATION OF L-TYPE CALCIUM CHANNEL FUNCTION IN CARDIAC MYOCYTES

饮食后多不饱和脂肪酸的抗心律失常作用 最近观察到心肌细胞膜的掺入 好几年了。其作用机制尚待确定。在这个项目中， 无膜多不饱和脂肪酸对体外培养细胞的影响 成年大鼠心肌细胞的研究(在体内，这些细胞可以被释放 磷脂酶作用后的心肌细胞膜)。现在 研究了DHA和花生四烯酸(AA；C20：4，n-6)o 全细胞电压钳L型钙、钾通道电导 细胞内游离钙荧光和收缩的实验与研究 成年大鼠心肌细胞负载Indo-1。尼群地平(10 NM)还原豌豆 ICa，由全细胞钳制从-40 mV到-5 mV测量，痉挛收缩 在细胞内测量的INDO-1钙荧光的幅度和相关 电刺激(0.5赫兹)。DHA(5FM)可消除上述效应，而AA可 不能阻断尼群地平的作用。10 nm BAYK8644的实验结果 在痉挛收缩和相关的胞浆钙离子增加中 由DHA预防，而不是AA(图2)。DHA或AA单独作用不明显。都不是 DHA或AA改变异丙肾上腺素(1，0.5，0.1fM)引起的ICa_o升高 抽动幅度。DHA取消了尼群地平或BAYK8644的作用，但 单独没有作用，表明它与钙离子通道结合 二氢吡啶结合部位并干扰ICA的调节 二氢吡啶类化合物。而DHA对内向整流电流(Ik1)没有影响 和延迟整流电流(Ik)，它加速了失活 瞬时外向钾电流(ITO)，并降低其幅度。这些 结果表明，选择性阻断Ito，也结合到 Omega-3多不饱和脂肪酸诱导心肌细胞二氢吡啶受体对激动剂的保护作用 钙超载和缺血引起的心律失常。此操作可能是 参与鱼油饲料体内抗心律失常作用的研究 动物模型和患有冠状动脉疾病的人类。

Antiarrhythmic effects of polyunsaturated fatty acids following dietary incorporation into cardiac cell membranes have been observed in recent years. The mechanisms of action are yet to be defined. In this project the effect of membrane-free polyunsaturated fatty acids delivered to isolated adult rat cardiac myocytes was investigated (in vivo these can be released from cardiac cell membranes following phospholipase action). The present study investigates the effects of DHA and arachidonic acid (AA;C20:4,n-6) o L-type calcium and K+ channel conductance in whole cell voltage-clamp experiments and on cytosolic free calcium fluorescence and contraction in adult rat indo-1 loaded cardiac myocytes. Nitrendipine (10 nM) reduced pea ICa, measured by whole cell clamp from -40 to -5 mV, twitch contraction amplitude and associated cytosolic indo-1 Ca2+ fluorescence measured during electrical stimulation (0.5Hz). DHA (5fM) abolished these effects but AA di not block the nitrendipine effects. Experiments with 10nM BAYK8644 resulted in increased twitch contraction and related cytosolic calcium which could b prevented by DHA but not AA (Fig2). DHA or AA alone had no effect. Neither DHA nor AA altered isoproterenol (1, 0.5, 0.1fM) induced increases in ICa o twitch amplitude. That DHA abolishes nitrendipine or BAYK8644 effects but has no effect alone, suggests that it binds to Ca2+ channels near dihydropyridine binding sites and interferes with ICa modulation by dihydropyridines. While DHA has no effect on inward rectifier current (Ik1 and delayed rectifier current (Ik) it accelerates the inactivation of transient outward K+ current (Ito) and decreases its magnitude. These results suggest that selective blockade of Ito and also binding to the dihydropyridine receptor in heart cells by omega-3 PUFA may protect agonist Ca2+ overload and ischemia induced arrhythmias. This action may be involved in the antiarrhythmic effects of fish oil diet in vivo both in animal models and in humans with coronary artery disease.