Myosin light chain kinase phosphorylation in swine carotid artery contraction and relaxation

D. A. Van Riper, B. A. Weaver, J. T. Stull, C. M. Rembold

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31 Scopus citations


We investigated the role of myosin light chain kinase (MLCK) phosphorylation in regulating the sensitivity of vascular smooth muscle myosin light chain (MLC) phosphorylation to intracellular Ca2+ concentration ([Ca2+](i)). 32PO4-loaded swine carotid arteries were stimulated with histamine or high K+, MLCK was isolated, and the relative phosphorylation of tryptic peptides was measured. In nonlabeled tissues, we measured [Ca2+](i) with aequorin, MLCK activity ratio, MLC phosphorylation, and force. A comparison of MLCK phosphorylation on peptide A (mol P in site A/mol MLCK) and MLCK activity ratio showed an inverse relation, suggesting that MLCK site A phosphorylation can regulate the Ca2+ sensitivity of MLCK. MLCK site A phosphorylation and MLCK activity ratio depended on [Ca2+](i). Histamine stimulation yielded greater MLC phosphorylation than high K+ stimulation over a range of [Ca2+](i); however, there were no apparent stimulus-dependent differences in MLCK phosphorylation, suggesting that stimulus-dependent differences in the Ca2+ sensitivity of MLC phosphorylation are not based on differences in MLCK phosphorylation. We also determined whether MLCK phosphorylation was involved in adenosine 3',5'- cyclic monophosphate-mediated relaxation. In histamine-contracted tissues, forskolin decreased [Ca2+](i), MLC phosphorylation, and force. MLCK phosphorylation decreased to an extent consistent with the decrease in [Ca2+](i). In KCl-stimulated tissues, forskolin did not alter [Ca2+](i) or increase MLCK phosphorylation but forskolin did decrease MLC phosphorylation. Thus, in swine carotid artery, MLCK phosphorylation appears to be regulated exclusively by Ca2+ and plays little role in stimulus- dependent differences in Ca2+ sensitivity of MLC phosphorylation or in mediating forskolin-induced relaxation.

Original languageEnglish (US)
Pages (from-to)H2466-H2475
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Issue number6 37-6
StatePublished - 1995


  • adenosine 3',5'-cyclic monophosphate
  • forskolin
  • intracellular calcium concentration
  • myosin light chain phosphorylation
  • vascular smooth muscle

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)


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