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Pulmonary vein contracts in response to hypoxia
Y Zhao1, C S Packer, R A Rhoades
1Department of Physiology and Biophysics, Indiana University School of Medicine, Indianapolis 46202-5120.
The American Journal of Physiology
|July 1, 1993
Summary
Pulmonary veins contract more strongly to hypoxia than pulmonary arteries. This venous hypoxic contraction is independent of the endothelium and calcium channels, unlike arterial responses.
Area of Science:
- Cardiovascular Physiology
- Pulmonary Circulation
- Hypoxia Research
Background:
- Hypoxic pulmonary vasoconstriction (HPV) is crucial for matching lung ventilation and blood flow.
- While arterial HPV is well-studied, pulmonary venous responses to hypoxia remain largely uninvestigated.
Purpose of the Study:
- To investigate if isolated rat pulmonary veins contract in response to low oxygen levels (hypoxia).
- To compare the hypoxic response of pulmonary veins with that of pulmonary arteries.
Main Methods:
- Isolated rat pulmonary artery and vein rings were subjected to hypoxia after precontraction.
- Isometric force transducers measured contractile responses under varying conditions (e.g., Ca(2+)-free media, endothelium denudation).
Main Results:
- Pulmonary veins exhibited a sustained contraction to hypoxia, distinct from the pulmonary artery's biphasic response.
- Venous hypoxic contraction magnitude exceeded both phases of the arterial response.
- Venous response was endothelium-independent but influenced by precontractile tone and agonist type.
- Venous contraction was inhibited by Ca(2+)-free media and calcium channel blockers, similar to arterial phase 2.
Conclusions:
- Pulmonary venous smooth muscle demonstrates a significant contractile response to severe hypoxia.
- This venous response is greater than that of the pulmonary artery.
- The pulmonary venous hypoxic response is endothelium-independent, with calcium channel involvement.