兴奋β_3受体对快速心房起搏家兔心房肌细胞I_(Ca,L)的影响

Effect of stimulating β_3-adrenergic receptors on L-type calcium current in atrial myocytes of rapid atrial pacing rabbits

目的：观察兴奋β3肾上腺素能受体（β3受体）对快速心房起搏（rapid atrial pacing,RAP）家兔心房肌细胞L型钙电流（ICa,L）的影响,为探索心房颤动（AF）的发病机制及治疗提供新的思路。方法：35只210～215kg家兔随机分组：1.离体部分：①假手术组（Sham组,n=7）：单纯开胸、安装起搏器不予起搏,1周后分离心房肌细胞,记录ICa,L（Sham组）。②手术组（n=7）：以600次/minRAP1周后,分离心房肌细胞,记录ICa,L（RAP组）;向细胞中加入B1、B2受体阻滞剂Nadolol及β3受体激动剂BRL37344（BRL）,记录ICa,L（RAP＋BRL组）;再加入β3受体特异性阻滞剂SR59230A（SR）,记录ICa,L（RAP＋BRL＋SR组）。2.在体部分：①RAP组（n=7）：单纯RAP1周;②RAP＋BRL组（n=7）：RAP后给予Nadolol及BRL1周;③RAP＋BRL＋SR组（n=7）：RAP后给予Nadolo、lBRL及SR1周。测定各组心房肌一氧化氮（NO）、环-磷酸鸟苷（cGMP）的含量及cGMP依赖性蛋白激酶（PKG）蛋白的表达。结果：①与Sham组相比,RAP组ICa,L明显减小（P〈0101）;②与RAP组相比,RAP＋BRL组ICa,L明显减小（P〈0101）,NO、cGMP的含量及PKG蛋白的表达明显增加（均为P〈0105）。③与RAP＋BRL组相比,RAP＋BRL＋SR组ICa,L明显增大（P〈0101）,NO、cGMP的含量及PKG蛋白的表达明显减少（P〈0101,P〈0101,P〈0105）。结论：兴奋β3受体可激活NO-cGMP-PKG通路并同时减小RAP家兔心房肌细胞ICa,L。

AIM ： To investigate the effect of stimulating β3-adrenergic receptors （β3-ARs） on L-type calcium current （ICL） in atrial myocytes of rapid atrial pacing （RAP） rabbits. METHODS： Thirty seven rabbits （2.0 - 2.5 kg） were randomly divided ： for ex vivo study in sham-operated group （ sham group, n = 7）, thoracotomy was performed and pacemakers were implanted but not paced. Atrial myocytes were isolated after 1 week and Ic,,L was recorded （sham group）. In the operation group （n = 7） , rabbits were paced at 600 beats per minute for 1 week, atrial myocytes were isolated and was recorded （ RAP group）. Atrial myocytes were then treated with β3, β3-ARs blocker nadolol and β3-ARs agonist BRL 37344 （BRL） and Ic,L was recorded （RAP ＋ BRL group）. Finally, atrial myocytes were incubated by β3-ARs selective antagonist SR 59230A （SR） and IcaL was recorded （RAP ＋ BRL ＋ SR group）. For in vivo study ： RAP group （ n = 7） with RAP for I week, RAP ＋ BRL group （ n = 7 ） with RAP plus nadolol and BRL for 1 week, and RAP ＋ BRL ＋ SR group （n = 7） with RAP plus nadolol, BRL and SR for 1 week. Nitric oxide （NO）, cyclic guanosine monophosphate （cGMP） and the protein expressions of cGMP-dependent protein kinases （PKG） were measured in each group. RESULTS： Compared with thatin sham group, the density of ICa,L obviously decreased in the RAP group （P 〈 0. 01 ） and compared with those in RAP group, the density of Ica,L obviously decreased （P 〈0.01 ） and the NO production, cGMP content and PKG protein expression obviously increased in RAP ＋ BRL group （ P 〈 0. 05 ）. Compared with those in the RAP ＋ BRL group, the density of Ica,L obviously increased （P 〈0.01 ） and NO production, cGMP content and PKG protein expression obviously decreased in RAP ＋ BRL ＋ SR group （P 〈0. 01, P 〈 0. 01, P 〈 0. 05）. CONCLUSION： Activation of β3-ARs decreases Ica,L in RAP rabbit atrial myocytes accompanied by stimulation of NO-cGMP-PKG signal pathway.