title: Optimization of isolated perfused/ventilated mouse lung to study hypoxic pulmonary vasoconstriction.
abstract: Hypoxic pulmonary vasoconstriction (HPV) is a compensatory physiological mechanism in the lung that optimizes the matching of ventilation to perfusion and thereby maximizes gas exchange. Historically, HPV has been primarily studied in isolated perfused/ventilated lungs; however, the results of these studies have varied greatly due to different experimental conditions and species. Therefore, in the present study, we utilized the mouse isolated perfused/ventilated lung model for investigation of the role of extracellular Ca(2+) and caveolin-1 and endothelial nitric oxide synthase expression on HPV. We also compared HPV using different perfusate solutions: Physiological salt solution (PSS) with albumin, Ficoll, rat blood, fetal bovine serum (FBS), or Dulbecco's Modified Eagle Medium (DMEM). After stabilization of the pulmonary arterial pressure (PAP), hypoxic (1% O2) and normoxic (21% O2) gases were applied via a ventilator in five-minute intervals to measure HPV. The addition of albumin or Ficoll with PSS did not induce persistent and strong HPV with or without a pretone agent. DMEM with the inclusion of FBS in the perfusate induced strong HPV in the first hypoxic challenge, but the HPV was neither persistent nor repetitive. PSS with rat blood only induced a small increase in HPV amplitude. Persistent and repetitive HPV occurred with PSS with 20% FBS as perfusate. HPV was significantly decreased by the removal of extracellular Ca(2+) along with addition of 1 mM EGTA to chelate residual Ca(2+) and voltage-dependent Ca(2+) channel blocker (nifedipine 1 μM). PAP was also reactive to contractile stimulation by high K(+) depolarization and U46619 (a stable analogue of thromboxane A2). In summary, optimal conditions for measuring HPV were established in the isolated perfused/ventilated mouse lung. Using this method, we further confirmed that HPV is dependent on Ca(2+) influx.
authors.affiliation: Department of Medicine, Section of Pulmonary, Critical Care, Sleep and Allergy Medicine, University of Illinois at Chicago, Chicago, Illinois, USA.
authors.forename: Hae Young
authors.initials: HY
authors.lastname: Yoo
authors.forename: Amy
authors.initials: A
authors.lastname: Zeifman
authors.forename: Eun A
authors.initials: EA
authors.lastname: Ko
authors.forename: Kimberly A
authors.initials: KA
authors.lastname: Smith
authors.forename: Jiwang
authors.initials: J
authors.lastname: Chen
authors.forename: Roberto F
authors.initials: RF
authors.lastname: Machado
authors.forename: You-Yang
authors.initials: YY
authors.lastname: Zhao
authors.forename: Richard D
authors.initials: RD
authors.lastname: Minshall
authors.forename: Jason X-J
authors.initials: JX
authors.lastname: Yuan
keywords: endothelial nitric oxide synthase; hypoxia; mouse lung; pulmonary artery; pulmonary vasoconstriction