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目的研究犬左心室壁外膜层、中层(M细胞)及内膜层细胞的L型钙电流大小,观察氯化镉阻断钙电流后,三层心肌单个细胞跨膜动作电位的变化。方法应用膜片钳全细胞记录技术。结果去极电压为+10mv时,I_(Ca,L)电流的峰值达最大,在心外膜、M细胞及心内膜细胞间存在显著差异,分别为-4.0±1.2、-5.3±0.4及-4.3±1.2pA/pF,(P<0.05)。在其它去极电压,三层细胞钙电流值无显著差异。氯化镉(0.2mM)使三层细胞动作电位均缩短,心内膜、M细胞及心外膜细胞APD_(90)分别由用药前的436.4±39.0ms,511.6±48.7ms,431.8±42.36ms缩短至用药后的293.4±41.7,296.7±50.3,295.2±40.9ms,APD_(90)分别缩短32.8％,42.0％,31.6％(P<0.05)。结论犬心室外膜、中层(M细胞)及内膜细胞的L型钙电流分布的差异性。
Objective To investigate the L-type calcium current in the outer, middle and inner tunica parietal canines, and observe the changes of the transmembrane action potentials of single cells in the three layers of myocardium after blocking the calcium currents with cadmium chloride. Methods Patch clamp whole cell recording technology. Results The peak value of I_ (Ca, L) current reached the maximum when the voltage was +10 mV, and there were significant differences between epicardial, M cells and endocardial cells, which were -4.0 ± 1.2, -5.3 ± 0.4 and - 4.3 ± 1.2 pA / pF, (P <0.05). In other depolarization voltage, three-layer cell calcium current value was no significant difference. The action potentials of three layers of cells were shortened by cadmium chloride (0.2mM). The APD_ (90) of endocardial, M cells and epicardial cells were decreased from 436.4 ± 39.0ms, 511.6 ± 48.7ms, 431.8 ± 42.36ms Shortened to 293.4 ± 41.7, 296.7 ± 50.3, 295.2 ± 40.9 ms and APD 90 decreased by 32.8%, 42.0% and 31.6%, respectively (P <0.05). Conclusions The differences of L-type calcium current distribution in canine outer membrane, middle layer (M-cell) and intima cells were observed.