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Effects of substrate and inhibition of oxidative metabolism on contraction and myosin phosphorylation in ASM.
- Source :
-
The American journal of physiology [Am J Physiol] 1993 Jun; Vol. 264 (6 Pt 1), pp. L553-9. - Publication Year :
- 1993
-
Abstract
- Steady-state active stress in smooth muscle is maintained by cross bridges which undergo continuous cycling and myosin phosphorylation, and the two processes both consume ATP. In this study, we investigated whether energy utilization by cross-bridge cycling and myosin phosphorylation is compartmentalized and examined their relative affinities for ATP in airway smooth muscle. We measured active stress, myosin phosphorylation, O2 consumption, and tissue ATP content in bovine tracheal smooth muscle activated by K+ depolarization when glucose was replaced by pyruvate and when oxidative metabolism was inhibited by hypoxia or uncoupled by 2,4-dinitrophenol. The results indicate that ATP produced from both glycolysis and oxidative metabolism is available to both cross-bridge cycling and myosin phosphorylation. However, steady-state myosin phosphorylation was insensitive to the inhibition of oxidative metabolism by hypoxia and mitochondrial uncoupling when steady-state isometric stress and tissue ATP content were significantly reduced. These results suggest that, relative to actomyosin adenosine 5'-triphosphatase, myosin light chain kinase has a higher affinity for ATP in intact airway smooth muscle. However, peak myosin phosphorylation associated with the initial rapid stress development was sensitive to inhibition of oxidative metabolism, probably reflecting a lower content of intracellular calcium store as a result of metabolic inhibition.
- Subjects :
- 2,4-Dinitrophenol
Analysis of Variance
Animals
Cattle
Dinitrophenols pharmacology
Glucose pharmacology
Hypoxia metabolism
Isometric Contraction
Oxidation-Reduction drug effects
Phosphorylation
Pyruvates pharmacology
Pyruvic Acid
Reference Values
Muscle Contraction
Muscle, Smooth metabolism
Myosins metabolism
Trachea metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 0002-9513
- Volume :
- 264
- Issue :
- 6 Pt 1
- Database :
- MEDLINE
- Journal :
- The American journal of physiology
- Publication Type :
- Academic Journal
- Accession number :
- 8333548
- Full Text :
- https://doi.org/10.1152/ajplung.1993.264.6.L553