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Hypoxic vasoconstriction in rat pulmonary and mesenteric arteries
R M Leach1, T P Robertson, C H Twort
1Respiratory Research Laboratories, United Dental School, London, United Kingdom.
The American Journal of Physiology
|March 1, 1994
Summary
Hypoxia causes a biphasic vasoconstriction in rat pulmonary arteries. Phase 1 is partly endothelium-dependent, while phase 2 relies entirely on the endothelium, suggesting new constrictor factors.
Area of Science:
- Cardiovascular Physiology
- Pulmonary Circulation
- Vascular Biology
Background:
- Hypoxic pulmonary vasoconstriction (HPV) is a critical physiological response.
- The precise mechanisms and endothelial dependence of HPV remain incompletely understood.
Purpose of the Study:
- To investigate the biphasic nature of hypoxic vasoconstriction in rat pulmonary and mesenteric arteries.
- To elucidate the role of the endothelium in different phases of the hypoxic response.
Main Methods:
- Isolated large and small pulmonary and mesenteric arteries from rats were used.
- Hypoxia (PO2 ~33 mmHg) was applied to pre-contracted arteries.
- Mechanical disruption of endothelium and pharmacological inhibitors were employed.
Main Results:
- Hypoxia induced a biphasic response in pulmonary arteries: a transient contraction (Phase 1) followed by a sustained contraction (Phase 2).
- Mesenteric arteries showed Phase 1 but relaxation instead of Phase 2.
- Phase 1 was partially endothelium-dependent in small arteries, while Phase 2 was abolished by endothelial disruption.
- Verapamil reduced Phase 1 and abolished Phase 2.
Conclusions:
- Rat pulmonary arteries exhibit a distinct biphasic response to hypoxia.
- Phase 1 of HPV is partially dependent on the endothelium, whereas Phase 2 is fully dependent.
- These findings suggest the involvement of endothelium-derived constricting factors in HPV.