ATP hydrolysis during contraction of permeabilized airway smooth muscle

Keith A. Jones, Robert R. Lorenz, Y. S. Prakash, Gary C. Sieck, David O. Warner

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


This study determined whether the time-dependent decline in the rate of ATP hydrolysis by actomyosin ATPase during sustained isometric force can occur in the absence of a time-dependent decline in regulatory myosin light chain (rMLC) phosphorylation in Triton X-100-permeabilized canine tracheal smooth muscle. Maximal activation with 10 μM Ca2+ induced sustained increases in isometric force, stiffness, and rMLC phosphorylation; however, the increase in the ATP hydrolysis rate was initially high but then declined to a steady-state level above that of the unstimulated muscle (basal 31.8 ± 5.8 nmol·cm-3·S-1; peak 81.4 ± 11.3 nmol · cm-3 · s-1; steady- state 62.2 ± 9.1 nmol·cm-3·S-1). Activation of strips in which the rMLC was irreversibly and maximally thiophosphorylated with adenosine 5'-O- (3-thiotriphosphate) also induced sustained increases in isometric force and stiffness but a nonsustained increase in ATP hydrolysis rate. There was no significant difference in the peak or steady-state isometric force, stiffness, or ATP hydrolysis rate or in the steady-state maximum unloaded shortening velocity between strips activated by 10 μM Ca2+ or rMLC thiophosphorylation (0.058 ± 0.016 and 0.047 ± 0.011 muscle lengths/s, respectively). Mechanisms other than changes in rMLC phosphorylation contribute to the time-dependent decline in actomyosin ATPase activity during sustained activation of canine tracheal smooth muscle.

Original languageEnglish (US)
Pages (from-to)L334-L342
JournalAmerican Journal of Physiology - Lung Cellular and Molecular Physiology
Issue number2 21-2
StatePublished - Aug 1999


  • Actomyosin adenosine 5'- triphosphatase activity
  • Adenosine 5'-triphosphate
  • Cross bridges
  • Latch bridges
  • Maximum unloaded shortening velocity

ASJC Scopus subject areas

  • Physiology
  • Pulmonary and Respiratory Medicine
  • Physiology (medical)
  • Cell Biology


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