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The Effects of [K + ] O on Regional Differences in Electrical Characteristics of Ventricular Myocytes in Guinea‐Pig
Author(s) -
Wan Xiaoping,
Bryant Simon M.,
Hart George
Publication year - 2000
Publication title -
experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0958-0670
DOI - 10.1111/j.1469-445x.2000.02048.x
Subject(s) - repolarization , myocyte , endocardium , medicine , chemistry , guinea pig , microfold cell , cardiology , biophysics , electrophysiology , biology , antigen , immunology
Altering [K+]o might have different effects on action potential duration (APD) in myocytes from different regions. Therefore, the effects of [K+]o on regional differences in action potential characteristics were investigated in sub‐endocardial, mid‐myocardial and sub‐epicardial myocytes isolated from the base of guinea‐pig left ventricular free wall using three different [K+]o (2.7, 5.4 and 8.1 mM KCl). Action potentials were recorded using the switch‐clamp technique at 0.5 Hz. Increasing [K+]o from 2.7 to 8.1 mM shortened the action potential duration to 90% repolarization (APD90; mean APD90 values in sub‐endocardial, mid‐myocardial and sub‐epicardial myocytes were, respectively, 295 +‐ 9, 286 +‐ 9 and 266 +‐ 8 ms in 2.7 mM [K+]o, 270 +‐ 7, 255 +‐ 7 and 215 +‐ 7 ms in 5.4 mM [K+]o, 234 +‐ 7, 212 +‐ 10 and 155 +‐ 8 ms in 8.1 mM [K+]o), depolarized the resting potential, and reduced the amplitude of the action potential. The effect of increasing [K+]o on action potential characteristics was more pronounced in sub‐epicardial myocytes than in sub‐endocardial and mid‐myocardial myocytes. The regional differences in APD90 in 5.4 mM [K+]o were increased in 8.1 mM [K+]o and abolished in 2.7 mM [K+]o. In conclusion, changing [K+]o produces more pronounced effects on action potentials in sub‐epicardial myocytes than in sub‐endocardial myocytes, modifying the normal heterogeneity of action potentials. The differences in the response of sub‐epicardium and sub‐endocardium to [K+]o may contribute to the flattening or inversion of the T wave commonly seen in patients presenting with hypokalaemia and the upright and tall T waves observed in electrocardiograms recorded during hyperkalaemia, although the underlying ionic currents remain to be determined.