title: Postnatal adrenoreceptor maturation in porcine intrapulmonary arteries.
abstract: The effect of postnatal age on norepinephrine-induced alpha 2-adrenoreceptor-mediated release of endothelium-derived relaxing factor in porcine intramuscular pulmonary arteries was studied. Rings of pulmonary artery from fetal, newborn, 3-d-, 10-d-, 9-wk-, and 15-wk-old pigs with and without endothelium were suspended for isometric force measurement in Krebs-Ringer bicarbonate solution (37 degrees C, 95% O2-5% CO2). In 15- and 10-wk-old pigs, norepinephrine increased tone in arteries with and without endothelium but produced relaxations at high concentrations only in arteries with endothelium. These relaxations were not inhibited by the alpha 1-antagonist prazosin but were completely abolished by the alpha 2-antagonist yohimbine and the inhibitor of nitric oxide release N-omega-nitro-L-arginine methyl ester. This confirms that the norepinephrine-induced relaxations were due to alpha 2-mediated release of endothelium-derived relaxing factor. Arteries from only 50% of the 10-d-old animals showed endothelium-dependent relaxations, and at 3 d of age and younger no relaxations were seen. In animals less than 10 d old, only some of the vessels contracted to norepinephrine and the contractile response was diminished compared with 15-wk-old animals, whereas the response to prostaglandin F2 alpha and histamine was similar in the neonatal group (newborn, 3 d old, and 10 d old). This group showed a dose-dependent relaxation to nitric oxide, with 10-d-old animals more sensitive to nitric oxide than newborn animals.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Vascular Biology and Pharmacology Unit, Institute of Child Health, London, United Kingdom.
authors.forename: L E
authors.initials: LE
authors.lastname: Wilson
authors.forename: M
authors.initials: M
authors.lastname: Levy
authors.forename: K
authors.initials: K
authors.lastname: Stuart-Smith
authors.forename: S G
authors.initials: SG
authors.lastname: Haworth
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D015237:Dinoprost / Q000494:pharmacology; D005333:Fetus / Q000378:metabolism; D006632:Histamine / Q000494:pharmacology; D066298:In Vitro Techniques; D009569:Nitric Oxide / Q000378:metabolism / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D011651:Pulmonary Artery / Q000187:drug effects / Q000254:growth & development* / Q000502:physiology*; D018341:Receptors, Adrenergic, alpha-2 / Q000187:drug effects / Q000378:metabolism*; D013552:Swine; D014661:Vasoconstriction / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects
chemical_list: D018341:Receptors, Adrenergic, alpha-2; D009569:Nitric Oxide; D006632:Histamine; D015237:Dinoprost; D009638:Norepinephrine