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      Relation between Extracellular Potassium Ion Concentration and Contracture Force after Abolition of Spike Discharge in Isolated Rat Portal Vein


      Journal of Vascular Research

      S. Karger AG

      Rat portal vein, Cooling, Potassium contracture, Calcium

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          Spontaneous electrical and mechanical activity of isolated rat portal vein was abolished by cooling to 10°C as indicated by sucrose gap recordings. Graded increases in [K<sup>+</sup>]<sub>o</sub> at this temperature caused only transient propagated activity after which the muscle stabilized at constant membrane potentials and contracture tensions. Complete relaxation occurred on return to normal [K<sup>+</sup>]<sub>o</sub>. An S-shaped relation was found between log [K<sup>+</sup>]₀ and contracture force; the mechanical threshold corresponded to about 9 mM K<sup>+</sup> and the maximal response was reached at 40-50 mM. Variations in [Ca<sup>2+</sup>]<sub>o</sub> from 0.4 to 12.5 mM did not appreciably affect the relative concentration-effect curve for K<sup>+</sup>. Thus a graded relation between depolarization and contractile force has been demonstrated in this normally spike-generating smooth muscle.

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          Author and article information

          J Vasc Res
          Journal of Vascular Research
          S. Karger AG
          18 September 2008
          : 11
          : 3
          : 120-127
          Department of Physiology and Biophysics, University of Lund, Lund
          158006 Blood Vessels 1974;11:120–127
          © 1974 S. Karger AG, Basel

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          Page count
          Pages: 8
          Research Paper


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