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KMID : 0948320050050010001
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Konyang Medical Journal
2005 Volume.5 No. 1 p.1 ~ p.6
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Relation Between Membrane Potential and Contractile Response in Thoracic Aorta Mesenteric Artery of Rat
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Kim Se-Hun
Chang Seok-Jong
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Abstract
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The membrane potential of vascular smooth muscle is a critical factor for determining vascular contractility. K+ permeability and extracellular K+ concentration are the most important contributors to the membrane potential and to Ca2+ influx and vascular contractility. In the present study, the relation between contractile responses and membrane potentials was investigated in different types of vessels, ie. thoracic aorta and mesenteric artery from Sprague- Dawley (SD) rat. Contractile responses to high K+-solution were measured using isometric tension recording in the thoracic aorta and mesenteric artery without endothelium. The contraction by high K+-solution was elicited at 10 mM and the maximum contraction was induced at 60 mM in both tissues. Calculated ED50 values of contractile responses to high K+-solution in the thoracic aorta and mesenteric artery were 18.6±1.7 and 27.5±0.6 mM, respectively. Membrane potentials were measured using whole cell patch clamp configuration in single smooth muscle cells. Cells were dialysised with a pipette solution containing 5 mM ATP and Ca2+ buffer, 0.1 mM EGTA. In normal PSS, resting membrane potentials measured in smooth muscle cells of aorta and mesenteric artery were -64.0±4.1 and -56.7±4.2 mV, respectively. When the contraction was elicited by 10 mM K+-solution, the membrane potentials were -54.0±4.3 and -46.8±4.3 mV in aorta and in mesenteric artery, respectively. The calculated membrane potentials of aortic smooth muscle cells and mesenteric arterial smooth muscle cells at ED50 of contractile response to high K+-solution were -46.4±2.0 and -34.1±0.4 mV, respectively. Membrane potentials at the maximal contraction were about -20 mV in both tissues. Further depolarization of membrane did not increase contractile response to K+. From the above result, it is suggested that the membrane potential may differ according to the anatomical site and size of the vessel and larger vessel is more reactive to membrane potential change than smaller vessel.
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KEYWORD
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artery, smooth muscle cell, membrane potential, contraction, rat
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