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Hypoxic constrictor response in the isolated pulmonary artery from chronically hypoxic rats
V S Karamsetty1, M R MacLean, K M McCulloch
1Department of Physiology and Pharmacology, University of Strathclyde, Glasgow, UK.
Respiration Physiology
|August 1, 1996
Summary
Pulmonary vasoconstriction response to severe acute hypoxia was reduced in rats with chronic hypoxia (CH) but normalized after 24-hour recovery. Endothelium function changes paralleled these pulmonary artery responses.
Area of Science:
- Physiology
- Cardiovascular Research
- Pulmonary Hypertension
Background:
- Chronic hypoxia (CH) alters pulmonary vascular responses.
- Understanding pulmonary artery ring behavior during hypoxia is crucial for cardiovascular research.
- Endothelium-dependent relaxation and nitric oxide (NO) pathways are key in regulating vascular tone.
Purpose of the Study:
- To characterize the acute hypoxia response in rat pulmonary artery rings after chronic hypoxia and recovery.
- To investigate the role of endothelium and nitric oxide (NO) in these responses.
- To assess changes in endothelium-dependent relaxation.
Main Methods:
- Isolated large intrapulmonary artery (IPA) rings from control, chronically hypoxic (CH), and post-hypoxic (PH) rats were used.
- Rings were precontracted and subjected to acute hypoxia (0% or 2% O2).
- Effects of endothelium removal and nitric oxide synthase inhibition (L-NOARG) were examined. Carbachol was used to assess relaxation.
Main Results:
- Pulmonary vasoconstriction to 0% O2 was significantly reduced in CH rats but normalized in PH rats.
- Hypoxia-induced vasoconstriction to 2% O2 was not different between groups.
- Endothelium removal and L-NOARG reduced contractile phases of hypoxia-induced vasoconstriction in control and CH rats.
- Carbachol-induced relaxation was attenuated in CH rats but normalized in PH rats.
Conclusions:
- Acute hypoxia-induced pulmonary vasoconstriction (HPV) to severe hypoxia (0% O2) is blunted in rats with chronic hypoxia.
- This blunted response and impaired endothelium-dependent relaxation are restored after 24 hours of recovery in room air.
- Findings highlight the dynamic changes in pulmonary artery function following chronic hypoxia and recovery.