Patency of the preterm fetal ductus arteriosus is regulated by endothelial nitric oxide synthase and is independent of vasa vasorum in the mouse.
Patency of the fetal ductus arteriosus (DA) is maintained in an environment of low relative oxygen tension and a preponderance of vasodilating forces. In addition to prostaglandins, nitric oxide (NO), a potent vasodilator in the pulmonary and systemic vasculatures, has been implicated in regulation of the fetal DA. To further define the contribution of NO to DA patency, the expression and function of NO synthase (NOS) isoforms were examined in the mouse DA on days 17-19 of pregnancy and after birth. Our results show that endothelial NOS (eNOS) is the predominant isoform expressed in the mouse DA and is localized in the DA endothelium by in situ hybridization. Despite rapid constriction of the DA after birth, eNOS expression levels were unchanged throughout the fetal and postnatal period. Pharmacological inhibition of prostaglandin vs. NO synthesis in vivo showed that the preterm fetal DA on day 16 is more sensitive to NOS inhibition than the mature fetal DA on day 19, whereas prostaglandin inhibition results in marked DA constriction on day 19 but minimal effects on the day 16 DA. Combined prostaglandin and NO inhibition caused additional DA constriction on day 16. The contribution of vasa vasorum to DA regulation was also examined. Immunoreactive platelet endothelial cell adhesion molecule and lacZ tagged FLK1 localized to DA endothelial cells but revealed the absence of vasa vasorum within the DA wall. Similarly, there was no evidence of vasa vasorum by vascular casting. These studies indicate that eNOS is the primary source of NO in the mouse DA and that vasomotor tone of the preterm fetal mouse DA is regulated by eNOS-derived NO and is potentiated by prostaglandins. In contrast to other species, mechanisms for DA patency and closure appear to be independent of any contribution of the vasa vasorum.
Richard
Charissa
C
Department of Pediatrics, University of Kansas Medical Center, Kansas City, KS 66160, USA.
Gao
Ju
J
LaFleur
Bonnie
B
Christman
Brian W
BW
Anderson
Judy
J
Brown
Naoko
N
Reese
Jeff
J
D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism / Q000502:physiology; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D004373:Ductus Arteriosus / Q000196:embryology*; D005314:Embryonic and Fetal Development; D004727:Endothelium / Q000196:embryology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005333:Fetus / Q000033:anatomy & histology / Q000502:physiology; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D008822:Mice, Transgenic; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D012333:RNA, Messenger / Q000378:metabolism; D014651:Vasa Vasorum / Q000196:embryology*; D014654:Vascular Patency / Q000502:physiology*
D016861:Cyclooxygenase Inhibitors; D004791:Enzyme Inhibitors; D012333:RNA, Messenger; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496315:Nos3 protein, mouse; D019331:NG-Nitroarginine Methyl Ester; D007213:Indomethacin