Fluorescein-labeled dextran concentration is increased in BAL fluid after ANTU-induced edema in rats

Several methodologies have been developed to assessalveolocapillary membrane permeability in acute lung injury. Thepurpose of this study was to determine the reliability of FITC-dextran compared with radioactive tracers to assess lung permeability alterations. After intraperitoneal administration of-naphthylthiourea (ANTU, 50 mg/kg) or DMSO-ANTU vehicle, the animalswere euthanized and their lungs were studied in an isolated-lungpreparation. FITC-dextran or radiolabeled tracers were added to theperfusate. At 2 h the bronchoalveolar lavage (BAL) fluid from the ANTUgroup showed a significantly greater amount of fluorescence in thesupernatant after centrifugation of BAL fluid compared with the DMSOgroup. Consistent results were observed with the radioactive tracers: there was an increase in extravascular albumin space and extravascular lung water compared with the control group. No cleavage of the FITCfrom the dextran molecule was evident by chromatography comparing samples recovered from the BAL fluid to the pure FITC-dextran molecule.In conclusion, measurement of FITC-dextran in the supernatant of BALfluid after intravascular administration is a reliable method ofassessing lung permeability changes in vivo and ex vivo.