Regulation of isotonic shortening velocity by second messengers in tracheal smooth muscle

S. J. Gunst, M. H. Al-Hassani, L. P. Adam

Research output: Contribution to journalArticle

28 Scopus citations


Evidence suggests that the mechanical behavior of smooth muscle tissues is regulated by Ca2+-dependent changes in the phosphorylation of the 20,000- Da light chain of myosin (MLC). However, alternative mechanisms activated by specific kinases may be involved in regulating the shortening velocity in some smooth muscle tissues. To determine how the activation of protein kinases A or C affects the regulation of the shortening velocity in canine tracheal smooth muscle, we evaluated the effects of forskolin (10-5 M) and phorbol 12,13-dibutyrate (PDBu, 3 x 10-6 M) on active stress, intracellular Ca2+ ([Ca2+](i)), MLC phosphorylation, and isotonic shortening velocity during contractions elicited by 60 mM KCl. Forskolin depressed and PDBu increased active stress, [Ca2+](i), MLC phosphorylation, and shortening velocity; thus the effects of these agents on the shortening velocity may result from changes in Ca2+-dependent MLC phosphorylation. In contrast, the decline in velocity that occurred with time during tonic contractions elicited by K+ depolarization was not associated with significant changes in MLC phosphorylation; thus the time-dependent changes in shortening velocity may be regulated by a mechanism other than MLC phosphorylation.

Original languageEnglish (US)
Pages (from-to)C684-C691
JournalAmerican Journal of Physiology - Cell Physiology
Issue number3 35-3
StatePublished - Jan 1 1994


  • contractile proteins
  • cross-bridge cycling
  • myosin light-chain phosphorylation
  • smooth muscle contraction

ASJC Scopus subject areas

  • Cell Biology
  • Clinical Biochemistry
  • Physiology

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