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1 Department of Pediatrics, Wake Forest University School of Medicine, Winston-Salem, NC, USA
2 Department of Pediatrics, Wake Forest University School of Medicine, Winston-Salem, NC, USA; Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Winston-Salem, NC, USA
3 Department of Pediatrics, Wake Forest University School of Medicine, Winston-Salem, NC, USA; Department of Surgery, Wake Forest University School of Medicine, Winston-Salem, NC, USA
* To whom correspondence should be addressed. E-mail: mfuloria{at}wfubmc.edu.
20-hydroxyeicosatetraenoic acid (20-HETE), a cytochrome P450 metabolite of arachidonic acid, is a vasoconstrictor in the systemic circulation and a vasodilator in the adult pulmonary circulation. Little is known about the vasoactive properties of 20-HETE in the newborn pulmonary circulation. The objectives of this study were to determine the vascular effects of 20-HETE and to explore the signaling mechanism(s) that mediate these effects in newborn pulmonary resistance-level arteries (PRA). Our findings demonstrate that, in contrast to the adult pulmonary circulation where 20-HETE mediates vasodilation, it causes constriction in newborn PRA at resting tone. Furthermore, inhibition of cyclooxygenase (COX) with indomethacin augments 20-HETE-induced constriction. The enhanced constrictor response to 20-HETE under conditions of COX inhibition is abolished in endothelium-disrupted PRA, suggesting that 20-HETE either stimulates endothelial-derived COX to release a counteracting vasodilator or is rapidly metabolized by COX to a less potent vasoconstrictor. 20-HETE-induced constriction is significantly inhibited by blocking calcium-dependent K+ (KCa) channels and the thromboxane-PGH2 receptor. Altogether, our data indicate that the vascular actions of 20-HETE are partially mediated via the activation of KCa channels and are significantly modulated by interactions with the COX-prostaglandin pathway.
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