Propofol Relaxes Extrapulmonary Artery but not Intrapulmonary Artery through Nitric Oxide Pathway

The object of this study was to compare vasorelaxing responses to propofol by the intrapulmonary artery (IPA) and the extrapulmonary artery (EPA), and to identify the mechanisms of action. Rat pulmonary arterial rings were isolated and suspended in organ chambers where isometric tension development was measured under optimal resting tension. All pulmonary arterial rings were pre-contracted with phenylephrine. Propofol (DiprivanTM) and the vehicle (10% IntralipidTM) were administered cumulatively in the presence or absence of Nω-nitro-L-arginine methyl ester (L-NAME). Sodium nitroprusside (SNP), a nitric oxide donor, was administered cumulatively. Propofol relaxed both EPA and IPA in a dose dependent manner (p<0.05), while the vehicle alone showed no effect. The vasorelaxing responses to propofol were significantly higher in EPA than IPA at higher concentrations (10-4 M and 10-4.5M) (p<0.05), and were decreased by L-NAME in EPA (p