Mendez C, Hernandez V
Department of Physiology, Centro de Investigacion y Estudios Avanzados del I. P. N., Mexico City, Mexico.
J Cardiovasc Electrophysiol. 2001 Mar;12(3):337-42. doi: 10.1046/j.1540-8167.2001.00337.x.
The present study was designed to examine the extent to which differences in input resistance contribute to the heterogeneity of excitability in canine endocardium.
The experiments were performed in isolated canine right anterior papillary muscles. The preparations were superfused with oxygenated Tyrode's solution at 36 degrees to 37 degrees C. Conventional methods were used for recording and stimulation. To obtain pertinent data, two microelectrodes were inserted into the same cell or into two contiguous cells. One microelectrode injected intracellular hyperpolarizing current to polarize the membrane; the second microelectrode recorded the changes in transmembrane potential. The two micreoelectrodes were separated by 8 to 10 microm. The procedure used provided input resistance and threshold current values for the doubly impaled cell or the two contiguous cell units. The same procedure was repeated at different sites of the preparation. The plot of input resistance versus threshold current showed a good fit (R2 = 0.97) between the experimental data and the curve for the rectangular hyperbola XY = 30 mV; therefore, the input resistance and the threshold current are inversely related.
The results indicate that the canine cardiac syncytium is nonhomogeneous with respect to input resistance and that input resistance is inversely related to the minimal current needed to reach threshold. Accordingly, the electrical excitability of the cells studied also is inhomogeneous.
本研究旨在探讨输入电阻的差异在多大程度上导致犬心内膜兴奋性的异质性。
实验在离体犬右前乳头肌上进行。标本在36℃至37℃下用含氧的台氏液灌流。采用常规方法进行记录和刺激。为获取相关数据，将两根微电极插入同一个细胞或两个相邻细胞中。一根微电极注入细胞内超极化电流使膜极化；另一根微电极记录跨膜电位的变化。两根微电极相距8至10微米。所采用的程序为双穿刺细胞或两个相邻细胞单元提供了输入电阻和阈值电流值。在标本的不同部位重复相同的程序。输入电阻与阈值电流的关系图显示实验数据与矩形双曲线XY = 30 mV的曲线拟合良好（R2 = 0.97）；因此，输入电阻与阈值电流呈负相关。
结果表明，犬心肌细胞在输入电阻方面是不均匀的，且输入电阻与达到阈值所需的最小电流呈负相关。相应地，所研究细胞的电兴奋性也是不均匀的。
