ATP hydrolysis during contraction of permeabilized airway smooth muscle.

Academic Article

Abstract

  • 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 microM Ca(2+) 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 microM Ca(2+) 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.
  • Authors

    Published In

    Keywords

  • Adenosine Triphosphate, Androstadienes, Animals, Dogs, Elasticity, Female, Hydrolysis, In Vitro Techniques, Isometric Contraction, Male, Muscle, Smooth, Myosin Light Chains, Permeability, Phosphorylation, Time Factors, Trachea, Wortmannin
  • Digital Object Identifier (doi)

    Author List

  • Jones KA; Lorenz RR; Prakash YS; Sieck GC; Warner DO
  • Start Page

  • L334
  • End Page

  • L342
  • Volume

  • 277
  • Issue

  • 2