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Pflügers Archiv

, Volume 338, Issue 4, pp 361–376 | Cite as

Effects of Ca-free and EDTA-containing Tyrode solution on transmembrane electrical activity and contraction in guinea pig papillary muscle

  • H. Tritthart
  • Don P. MacLeod
  • H. E. Stierle
  • H. Krause
Article

Summary

Guinea pig papillary muscle was exposed to Tyrode solution to which no Ca had been added (Ca-free) and to various concentrations of EDTA in either Tyrode or Ca-free Tyrode. The results were as follows:
  1. 1.

    During 15 to 20 min exposure to Ca-free Tyrode the force of contraction of papillary muscles initially declined rapidly and then at varying rates and to varying degrees. Action potential duration and resting potential were reduced but maximum upstroke velocity (dV/dtmax) was increased. The effects were essentially reversed upon Ca replacement.

     
  2. 2.

    Exposure to 0.8 mM EDTA in Ca-free Tyrode or 2.5 mM EDTA in Tyrode produced similar effects as exposure to Ca-free Tyrode although the rates of change were more rapid and contraction was always abolished.

     
  3. 3.

    Exposure to 2.5 or 5.0 mM EDTA in Ca-free Tyrode or 5 mM EDTA in Tyrode caused a very rapid loss of measurable contraction, a decrease in resting potential, a marked increase in action potential duration and an increase ind V/dtmax. Replacement of Ca caused a beat to beat decrease in action potential duration, an increase in resting potential, a decrease ind V/dtmax and often an increase in resting tension. Contraction was initiated within 15 to 20 sec associated with marked after-contractions. As the after-contraction amplitude declined there was a decrease in resting tension. Action potential duration and resting potential recovered during 10 to 15 min after Ca replacement altough plateau duration usually did not return to control value.

     

The results indicate that the effects of Ca removal on guinea pig ventricular muscle depend on the rate of removal. Transmembrane electrical changes are proposed to be the result of membrane permeability changes resulting in an increase in both general and Na-specific leakage. After-contractions are considered to be the result of intracellular Ca overload due to increased membrane permeability to Ca.

Key words

Mammalian Ventricle Transmembrane Electrical Activity Force of Contraction Ca-Deprivation EDTA 

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Copyright information

© Springer-Verlag 1973

Authors and Affiliations

  • H. Tritthart
    • 1
  • Don P. MacLeod
    • 1
  • H. E. Stierle
    • 1
  • H. Krause
    • 1
  1. 1.Physiologisches Institut der Universität Freiburg/Br.Freiburg/Br.West Germany

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