Pflügers Archiv

, Volume 412, Issue 3, pp 231–239 | Cite as

Influence of pH on isometric force development and relaxation in skinned vascular smooth muscle

  • Jeffrey P. Gardner
  • F. P. J. Diecke
Heart, Circulation, Respiration and Blood; Environmental and Exercise Physiologh


The effects of pH (from pH values 6.50–7.10) on isometric tension development and relaxation were investigated in Triton X-100 “skinned” rat caudal artery. Helically cut skinned strips contracted in 21 μM Ca2+ were studied with respect to maximal isometric tension (Po) and rate of contraction (T0.5C), and following relaxation in 18 nm Ca2+, the rate of relaxation (T0.5R). Acidic pH (pH 6.50) decreased Po to 87% of isometric force obtained at pH 6.90, and increased the rate of contraction as shown by a decrease of T0.5C to 80%. In contrast, T0.5R increased 4.5-fold, indicating that with a change of only 0.40 pH units, relaxation rates were dramatically decreased. pCa-tension curves at pH values 6.50, 6.70, 6.90 and 7.10 indicated no significant shift in half maximal activation (pCa50) between pH 6.50 and 6.70, but a significant (P<0.01) shift in pCa50 between pH 6.70 ([Ca2+]=0.46 μM) and pH 7.10 ([Ca2+]=0.87 μM). Compared to contractions at pH 6.90, myosin light chain (LC20) phosphorylation at pH 6.50 was significantly greater at 30 and 60 s into contraction but not significantly different at 3–10 min. At both pH 6.50 and 6.90, dephosphorylation was rapid and substantially preceded relaxation; LC20 dephosphorylation and relaxation occurred more rapidly at pH 6.90 than at 6.50. At pH 6.50 and 6.90, relax solutions made with increased Ca2+ buffering capacity showed no effect in enhancing T0.5R, suggesting the difference between relaxation rates was not due to Ca2+ diffusion limitations from the skinned strip. We suggest pH changes can after the contractile and relaxation responses in vascular smooth muscle and these effects may be related to LC20 phosphorylation/dephosphorylation regulatory mechanisms.

Key words

Intracellular pH Vascular smooth muscle Chemically skinned muscle Isometric force 20,000 Da myosin light chain phosphorylation “Ca2+ jumps” 



piperazine-N,N′-bis-(2-ethanesulfonic acid)


5-ethyleneglycol-bis-(β-aminoethyl ether)-N,N,N′,N′-tetraacetic acid




1,6-diaminohexane-N,N,N′,N′-tetraacetic acid


sodium dodecyl sulfate


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Copyright information

© Springer-Verlag 1988

Authors and Affiliations

  • Jeffrey P. Gardner
    • 1
  • F. P. J. Diecke
    • 1
  1. 1.Department of PhysiologyUMDNJ-New Jersey Medical SchoolNewarkUSA

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