Lipopolysaccharide-induced airway hyporeactivity to methacholine in guinea pigs in vivo is absent in the isolated, perfused trachea in vitro.
Johnston-RA; Olson-SG; Fedan-JS
FASEB J 2000 May; 14(8):A1497
This study examined the effects of lipopolysaccharide (LPS)-treatment (4 mg/kg, i.p., 18 hr post-exposure) on guinea pig reactivity to methacholine (MCh) in vivo and in vitro. In vivo airway reactivity to MCh was measured by placing conscious, guinea pigs in a two-chamber whole body plethysmograph for measuring specific airway resistance (SRaw) and exposing them to increasing concentrations of MCh aerosol. In LPS-treated animals, the basal SRaw was increased compared to that in the saline injected control animals. In addition, the LPS-treated animals were hyporeactive to inhaled MCh. Airway reactivity in vitro was measured using the isolated, perfused trachea preparation to permit MCh addition separately to the serosal (extraluminal; EL) or mucosal (intraluminal; IL) surfaces; because of the epithelium, EL reactivity to MCh is greater than IL reactivity. In epithelium-intact tracheas there was no difference in the EC50 values for contraction to EL and IL MCh between control- and LPS-treated guinea pigs. In epithelium-denuded tracheas where the difference between EL and IL reactivity was abolished, LPS-treatment had no effect on reactivity to MCh. These results suggest that the hyporeactivity observed in vivo does not involve the trachea or the mechanism(s) is lost in vitro.
Methacholines; Laboratory-animals; Animals; Animal-studies; In-vivo-studies; In-vitro-studies; Exposure-levels; Airway-resistance; Aerosols
Abstract; Conference/Symposia Proceedings
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