title: Maturational changes in endothelium-derived relaxations in newborn piglet pulmonary circulation.
abstract: It is accepted knowledge that the endothelium can profoundly affect vascular tone through the release of vasoactive substances. The maturational changes in the role of the endothelium-derived relaxing factor (EDRF) and ATP-dependent K+ channels in the neonatal pulmonary circulation were investigated in isolated perfused lungs from 1- and 7-day-old piglets. The EDRF inhibitor, N omega-nitro-L-arginine (L-NNA), had potent dose-dependent constrictor effects on the pulmonary vasculature with normal and raised tone. The constrictor effect of L-NNA was greater (P < 0.05) in the 1-day-old than in the 7-day-old lungs and was significantly (P < 0.005) attenuated by pretreatment with the EDRF precursor, L-arginine. Furthermore, we studied the possibility of developmental changes in the sensitivity of smooth muscle cells to EDRF by testing sodium nitroprusside, nitric oxide, and 8-bromoguanosine 3',5'-cyclic monophosphate (8-BrcGMP). All caused a decrease in perfusion pressure, but only sodium nitroprusside elicited a greater (P < 0.01) effect in the 1-day-old. Endothelin-1 (ET-1) and bradykinin (BK) elicited dilator responses that were significantly (P < 0.05) reduced in the presence of L-NNA. Interestingly, the dilator response to ET-1 was more marked (P < 0.001) in the younger group, whereas no age difference was noted with BK. Finally, lemakalim, a K+ channel activator, caused a vasodilation of equal magnitude at both ages. In summary, EDRF and ATP-dependent K+ channels appear to play a role in the control of the newborn piglet pulmonary vasculature.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Pediatrics, Montreal Children's Hospital, Quebec, Canada.
authors.forename: T
authors.initials: T
authors.lastname: Perreault
authors.forename: J
authors.initials: J
authors.lastname: De Marte
mesh_terms: D000375:Aging / Q000502:physiology; D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development* / Q000502:physiology; D016232:Endothelins / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000187:drug effects / Q000254:growth & development / Q000502:physiology*; D066298:In Vitro Techniques; D009569:Nitric Oxide / Q000502:physiology; D015221:Potassium Channels / Q000502:physiology; D011652:Pulmonary Circulation; D013552:Swine; D014664:Vasodilation; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D016232:Endothelins; D015221:Potassium Channels; D014665:Vasodilator Agents; D009569:Nitric Oxide