Purpose: 20-hydroxyeicosatetraenoic acid (20-HETE) may have physiologic significance in hemodynamic regulation being a potent vasoconstrictor in dog and cat renal microvasculature but a potent vasodilator in rabbit and human small pulmonary arteries. Arachidonic Acid (AA) is metabolized to 20-HETE by hydroxylation at the ω position by members of the 4A subfamily of cytochrome P450, specifically CYP 4A4 in rabbit lung. This enzyme has been cloned and expressed in E.coli in our lab. By immunohistochemical staining it has been localized to endothelial cells of the lung microvasculature. Our purpose was to show that a homologue of this enzyme exists in baboon lung and to compare activity of this enzyme in normal and hyperoxic injured baboon lung. Methods: Lung tissue was freshly harvested from injured baboons subjected to 100 % FiO2 and normal baboons. Lung microsomes were prepared by homogenization and sequential high speed centrifugation. Immunoblot procedure was done on separated microsomal proteins with a polyclonal antibody to CYP4A4. Assays to determine enzyme activity towards AA and other substrates were performed with the lung microsomes. Results: Bands identified by immunoblot indicated the probable presence of a cytochrome P450 ω hydroxylase. We confirmed activity towards AA to form 20-HETE. Substrate specificity with PGE1 suggested a homologue of the rabbit CYP4A4. Our data was inconclusive on the effect of hyperoxic lung injury on the efficiency in metabolizing AA and PGE1 although there was a trend towards increased activity with the injured lung. Conclusions: There exists a homologue to rabbit CYP4A4 in baboon lung that can convert AA to 20-HETE a potentially important vasoactive compound. Our studies on activity in injured versus normal lung was inconclusive in demonstrating a significant difference. Clinical Implications: This mammalian homologue of CYP4A4 may be an important enzyme in regulation of the pulmonary vasculature.
|Original language||English (US)|
|Issue number||4 SUPPL.|
|State||Published - Oct 1 1998|
ASJC Scopus subject areas
- Pulmonary and Respiratory Medicine
- Critical Care and Intensive Care Medicine
- Cardiology and Cardiovascular Medicine