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Oxygen sensors in vascular smooth muscle
Y Katayama1, R F Coburn, W S Fillers
1Department of Physiology, University of Pennsylvania School of Medicine, Philadelphia 19104.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|November 1, 1994
Summary
Cellular responses to low oxygen involve O2 sensors and signal transduction. This study in aortic smooth muscle suggests cytochrome aa3 acts as the O2 sensor, with increased inorganic phosphate aiding signal transduction.
Area of Science:
- Cellular Physiology
- Biochemistry
- Muscle Contraction
Background:
- Cellular functions are modulated by oxygen levels (PO2).
- Responses to decreased PO2 involve O2 sensing and signal transduction pathways.
- Aortic smooth muscle provides a model to study these oxygen-dependent mechanisms.
Purpose of the Study:
- To investigate the O2 sensor and signal transduction mechanisms in decreased PO2-evoked relaxations.
- To elucidate the role of phosphorylation potential and inorganic phosphate in oxygen sensing.
- To identify the specific O2 sensor involved in aortic smooth muscle relaxation.
Main Methods:
- Utilized norepinephrine-contracted aortic smooth muscle as an experimental model.
- Measured changes in phosphorylation potential and intracellular inorganic phosphate ([Pi]) concentrations.
- Assessed the kinetics of muscle relaxation under varying PO2 and [Pi] conditions.
Main Results:
- Decreased PO2 led to rapid relaxations in aortic smooth muscle.
- Phosphorylation potential decreased significantly at the onset of relaxation.
- Increased intracellular [Pi] accelerated relaxations at a constant phosphorylation potential, implicating [Pi] in transduction.
Conclusions:
- Results support cytochrome aa3 as the O2 sensor mediating PO2-evoked relaxations.
- An increase in intracellular [Pi] and a decrease in kinetic energy are implicated in the transduction mechanism.
- These findings provide insight into the biochemical pathways controlling cellular responses to hypoxia.