IN-VIVO MEASUREMENT OF NEUTROPHIL ACTIVITY IN EXPERIMENTAL LUNG INFLAMMATION

Positron emission tomography (PET) was used to quantify (18)fluorodeox yglucose ((18)FDG) uptake in rabbits with experimental pneumonitis loc alized to the right upper lobe. In Streptococcus pneumoniae-induced pn eumonia, which causes a profound inflammatory response lasting several days before it resolves,(18)FDG uptake was pronounced at 15 h after t he onset of inflammation, but by 48 h there was little uptake. in bleo mycin injury, which progresses from an acute inflammatory stage to chr onic inflammation and scarring, (18)FDG uptake detectable by PET persi sted for up to 21 d. Autoradiography of histologic sections after intr avenous administration of [H-3]deoxyglucose 15 h after streptococcal i nstillation and 2 wk after bleomycin instillation showed that, in both models, deoxyglucose uptake was localized to neutrophils. In the stre ptococcal model there was little (18)FGD signal at 6 h, when major neu trophil migration occurs. At 15 h, [H-3]deoxyglucose-labeled neutrophi ls were present in the airspaces but not in the alveolar septa, sugges ting that the deoxyglucose signal reflected a postmigratory neutrophil event, probably the respiratory burst. Thus, PET of (18)FDG uptake ma y provide a novel and readily repeatable, noninvasive approach to the in vivo study of neutrophil activity at otherwise inaccessible sites.