Related Experiment Videos
Hypoxic pulmonary vasoconstriction is modified by P-450 metabolites
1Department of Physiology, Cardiovascular Research Center, Milwaukee, 53226, Wisconsin, USA.
American Journal of Physiology. Heart and Circulatory Physiology
|September 29, 2000
Summary
Endogenous 20-hydroxyeicosatetraenoic acid (20-HETE) influences pulmonary vascular tone, especially during hypoxia. Inhibiting its synthesis increases pulmonary pressure and constricts arteries, suggesting 20-HETE is a key regulator.
Area of Science:
- Cardiovascular Physiology
- Pulmonary Circulation
- Arachidonic Acid Metabolism
Background:
- 20-Hydroxyeicosatetraenoic acid (20-HETE) is a cytochrome P-450 4A (CYP4A) metabolite of arachidonic acid (AA).
- 20-HETE is known to dilate human pulmonary arteries (PA), but its role in pulmonary vascular tone is not fully understood.
- The contribution of P-450 metabolites to pulmonary vascular tone requires further investigation.
Purpose of the Study:
- To investigate the role of endogenous 20-HETE in regulating pulmonary vascular tone, particularly under hypoxic conditions.
- To examine the effects of CYP4A omega- and omega1-hydroxylase inhibitors on pulmonary perfusion pressure and PA ring tone.
- To assess the expression of CYP4A protein in rabbit lung tissue.
Main Methods:
- Isolated rabbit lungs were ventilated with normoxic or hypoxic gases to measure perfusion pressures.
- Rabbit PA rings were used to assess changes in tone induced by 20-HETE and CYP4A inhibitors.
- Inhibitors of 20-HETE synthesis (17-oxydecanoic acid, N-methylsulfonyl-12,12-dibromododec-11-enamide) and an epoxygenase inhibitor (6-(20-propargyloxyphenyl)hexanoic acid) were administered.
- CYP4A protein expression was confirmed using immunospecific protein analysis.
Main Results:
- Hypoxia increased perfusion pressure in isolated rabbit lungs.
- Inhibitors of 20-HETE synthesis significantly increased baseline perfusion pressure and amplified hypoxia-induced pressure increases.
- 20-HETE relaxed phenylephrine-constricted PA rings, while its synthesis inhibitors enhanced contraction, indicating a vasodilatory role.
- Hypoxia and inhibitors blocked the conversion of AA to 20-HETE.
- CYP4A protein was expressed in male rabbit lung tissue.
Conclusions:
- Endogenously produced 20-HETE plays a significant role in modulating rabbit pulmonary vascular tone.
- 20-HETE acts as a pulmonary vasodilator, counteracting vasoconstriction, especially during hypoxic conditions.
- Inhibition of 20-HETE synthesis exacerbates pulmonary hypertension, highlighting its therapeutic potential.