乙酰胆碱对犬右室三层心肌细胞L型钙电流不均一性的影响

目的测定犬右室三层心肌细胞上的L型钙电流(ICa,L),并研究其对自主神经递质乙酰胆碱的反应。方法经酶解法分离获得犬右室三层心肌细胞,应用全细胞膜片钳技术,记录并比较三层心肌细胞的ICa,L,以及应用2μmol/L乙酰胆碱前后电流-电压曲线的差异。结果ICa,L的峰值电流密度外膜下大于M细胞,而M细胞又大于内膜下心肌细胞,分别为-4.896±1.907pA/pF(n=31),-3.406±0.904pA/pF(n=37),-2.788±0.756pA/pF(n=33)(P<0.05)。使用乙酰胆碱后,右室外膜下及M细胞的峰值电流密度减小-4.921±1.023pA/pF vs -3.462±0.997pA/pF(n=12);-3.803±1.115pA/pF vs -2.959±0.883pA/pF(n=13),P均<0.05]。心内膜下心肌细胞用药前后无差异(P>0.05)。结论ICa,L在犬右室三层心肌细胞存在不均一性,乙酰胆碱可以减小心外膜下、M细胞的ICa,L,对内膜下心肌细胞的ICa,L无影响。

Effect of acetylcholine on electrical heterogeneity of L-type calcium current in canine ventricular myocytes

Objective To examines the character of L-type calcium current (ICa,L) in three distinct canine ventricular myocytes and their response to acetylcholine (Ach). Methods Using whole-cell patch clamp techniques to investigate the electrophysiological characteristics of ICa,L of myocytes enzymatically dissociated from right canine ventricular epicardial, midmyocardial, and endocardial, and to compare the difference of current-voltage relations before and after using Ach. Results The peak density of ICa,L was -4.896±1.907 pA/pF(n=31), -3.406±0.904 pA/pF(n=37), -2.788±0.756 pA/pF(n=33), respectively in right ventricular (RV) epicardial, midmyocardial, and endocardial myocytes (P<0.05). Perfusion of Ach (2 μmol/L) decreased peak ICa,L densities from -4.921±1.023 pA/pF(n=12) to -3.462±0.997 pA/pF(P<0.05) in RV epicardial myocytes, -3.803±1.115 pA/pF(n=13) to -2.959±0.883 pA/pF(all P< 0.05) in RV midmyocardial myocytes, -2.445±0.986 pA/pF(n=11) to -2.510±1.003 pA/pF(P>0.05) in RV endocardial myocytes. Conclusion Ach can significantly decrease peak ICa,L densities on the epicardial cells and M cells, and the endocardial cells present no response to the drug, therefore Ach can increase outward shift in the current active at the end of phase 1 of the right ventricular epicardial action potential.