Regulation of the Ca2+ dependence of smooth muscle contraction

Da Chun Tang, James T. Stull, Yasutaka Kubota, Kristine E. Kamm

Research output: Contribution to journalArticlepeer-review

70 Scopus citations


Cellular mechanisms for the regulation of Ca2+-dependent myosin light chain phosphorylation were investigated in bovine tracheal smooth muscle. Increases in the free intracellular Ca2+ concentration ([Ca2+](i)), light chain phosphorylation, and force were proportional to carbachol concentration. K(CaM), the concentration of Ca2+/calmodulin required for half-maximal activation of myosin light chain kinase, also increased proportionally, presumably due to Ca2+-dependent phosphorylation of the kinase. Isoproterenol treatment inhibited agonist-induced contraction by decreasing [Ca2+](i) and thereby light chain phosphorylation. Depolarization by increasing concentrations of KCl also resulted in proportional increases in [Ca2+](i), K(CaM), light chain phosphorylation, and force. However, the [Ca2+](i) required to obtain a given value of either light chain phosphorylation or K(CaM) was greater in KCl-depolarized tissues compared to carbachol-treated tissues. In muscles contracted with KCl, isoproterenol treatment resulted in diminished light chain phosphorylation and force without alterations in [Ca2+](i) or K(CaM). Thus, isoproterenol inhibition of KCl-induced contraction results from a cellular mechanism different from that found in agonist-induced contraction. In neither case does isoproterenol produce relaxation by altering the calmodulin activation properties of myosin light chain kinase.

Original languageEnglish (US)
Pages (from-to)11839-11845
Number of pages7
JournalJournal of Biological Chemistry
Issue number17
StatePublished - 1992

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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