Abstract
The wide use of hyperkelemic solutions in cardiac surgery including heart transplantation draws our attention on the effect of hyperkalemia on large conductance calcium‐activated potassium channels (BKCa). The BKCa of arterial smooth muscle cells (SMCs) is pivotal in the regulation of vascular tone. SMCs were enzymatically isolated from porcine coronary arteries. Primary cultures of the SMCs (usually 5–7 days) were used for patch‐clamp study. The effect of K+ with different concentrations (5.4, 20, 60, or 120 mM) was investigated on whole‐cell BKCa current with a holding potential of −60 mV (n=5 for each concentration). The rise of extracellular K+ in bath solutions significantly resulted in increase of BKCa currents in a K+‐concentration dependent manner in comparison with the control solution (5.4mM: 31.6±3.4pA/pF; 20mM: 73.6±11.4pA/pF; 60mM: 108.6±20.6pA/pF; 120mM: 135.2±20.5 pA/pF, p<0.05 one‐way ANOVA). Raise of extracellular K+ concentration increases BKCa activity of the porcine coronary arterial SMCs in a dose‐dependent manner. This may be an important part of the effect of hyperkalemic cardioplegia on the coronary circulation and therefore may have clinical implications in the heart preservation.Acknowledgments: Supported by Hong Kong RGC grant (CUHK4383/03M) and CUHK direct grants (4450171, 4450231, 2041305)
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