title: Effects of changes in pH and CO2 on pulmonary arterial wall tension are not endothelium dependent.
abstract: We examined the changes in isolated pulmonary artery (PA) wall tension on switching from control conditions (pH 7.38 +/- 0.01, PCO2 32.9 +/- 0.4 Torr) to isohydric hypercapnia (pH change 0.00 +/- 0.01, PCO2 change 24.9 +/- 1.1 Torr) or normocapnic acidosis (pH change -0.28 +/- 0.01, PCO2 change -0.3 +/- 0.04 Torr) and the role of the endothelium in these responses. In rat PA, submaximally contracted with phenylephrine, isohydric hypercapnia did not cause a significant change in mean (+/- SE) tension [3.0 +/- 1.8% maximal phenylephrine-induced tension (Po)]. Endothelial removal did not alter this response. In aortic preparations, isohydric hypercapnia caused significant (P < 0.01) relaxation (-27.4 +/- 3.2% Po), which was largely endothelium dependent. Normocapnic acidosis caused relaxation of PA (-20.2 +/- 2.6% Po), which was less (P < 0.01) than that observed in aortic preparations (-35.7 +/- 3.4% Po). Endothelial removal left the pulmonary response unchanged while increasing (P < 0.01) the aortic relaxation (-53.1 +/- 4.4% Po). These data show that isohydric hypercapnia does not alter PA tone. Reduction of PA tone in normocapnic acidosis is endothelium independent and substantially less than that of systemic vessels.
authors.affiliation: Department of Human Anatomy and Physiology, University College, Dublin 2, Ireland.
authors.forename: M
authors.initials: M
authors.lastname: Sweeney
authors.forename: D
authors.initials: D
authors.lastname: Beddy
authors.forename: V
authors.initials: V
authors.lastname: Honner
authors.forename: B
authors.initials: B
authors.lastname: Sinnott
authors.forename: R G
authors.initials: RG
authors.lastname: O'Regan
authors.forename: P
authors.initials: P
authors.lastname: McLoughlin
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000138:Acidosis / Q000503:physiopathology; D000818:Animals; D002245:Carbon Dioxide / Q000097:blood; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology / Q000503:physiopathology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D006935:Hypercapnia / Q000503:physiopathology; D066298:In Vitro Techniques; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology / Q000503:physiopathology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D010656:Phenylephrine / Q000494:pharmacology; D011651:Pulmonary Artery / Q000187:drug effects / Q000502:physiology* / Q000503:physiopathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology*
chemical_list: D004791:Enzyme Inhibitors; D002245:Carbon Dioxide; D010656:Phenylephrine; D019001:Nitric Oxide Synthase; D000109:Acetylcholine; D019331:NG-Nitroarginine Methyl Ester