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A topographical study of mechanical and electrical properties of single myocytes isolated from normal guinea‐pig ventricular muscle
Author(s) -
Wan X.,
Bryant S. M.,
Hart G.
Publication year - 2003
Publication title -
journal of anatomy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.932
H-Index - 118
eISSN - 1469-7580
pISSN - 0021-8782
DOI - 10.1046/j.1469-7580.2003.00187.x
Subject(s) - myocyte , repolarization , depolarization , ventricle , medicine , cardiology , anatomy , chemistry , biophysics , electrophysiology , biology
Major regional differences in the electrical properties of myocytes from ventricular muscle have been described previously, on the basis of samples taken from a maximum of three regions in each heart. In order to define the topographical basis for such differences, we studied the electrical and mechanical properties of single myocytes isolated from 20 regions throughout the ventricles in the normal guinea‐pig heart. Single myocytes were isolated using an enzymatic dispersion method, and were studied under conditions that were close to physiological. Cell capacitance and action potentials were recorded using the switch‐clamp technique, and cell length and evoked shortening were measured using a photodiode array system. In the left ventricular free wall, mid‐myocardial cells were longer and had greater capacitative surface area than surface myocytes. There were transmural but not longitudinal differences in APD 90 (action potential duration to 90% repolarization), with the longest APD 90 in subendocardial and the shortest in subepicardial myocytes. We found a septum – left ventricular free wall – right ventricular free wall gradient, with the longest APD 90 in the septum and the shortest in the right ventricular free wall. The regional distribution of APD 90 was closely mirrored by relaxation time. Peak cell shortening was greater in subendocardial myocytes than in subepicardial myocytes in the left ventricular free wall, and in myocytes from the left side of the septum compared with the right. We concluded that the regional distribution of APD is closely and inversely related to the sequence of ventricular depolarization, and that the regional variations in cell shortening amplitude are related principally to reported regional variations in wall stress.