Single-tracer technique to evaluate pulmonary edema and its application to detect the effect of hexamethylene diisocyanate trimer aerosol exposures.

Two hours after a four-hour exposure to hexamethylene diisocyanate trimer (HDIt) aerosol between 2.5 and 39 mg/m3, mice were injected iv with 51Cr-EDTA (chromium ethylenediaminetetraacetate). Ten minutes later the lung was lavaged. A larger amount of 51Cr-EDTA was detected in the lung lavage of HDIt mice than of controls in a concentration-related fashion. The concentration-response curve was shifted to the left compared with that constructed using lung weight increase as response. Kinetic studies of the plasma level of 51Cr-EDTA revealed a three-exponential profile in normal mice, and similar plasma levels were obtained with mice exposed to 18-24 mg/m3 HDIt. However, both the amount of 51Cr-EDTA in the alveolar space and concentration in the pulmonary extravascular compartment were higher in HDIt-exposed mice than in controls. The data of 51Cr-EDTA distribution in the lung were fitted with a three-compartment model. According to the model, HDIt exposures increase the permeability constants of 51Cr-EDTA transport into the alveolar space from blood which accounts for the larger amount of 51Cr-EDTA in lung lavage of HDIt-exposed mice. This 51Cr-EDTA injection and lung lavage technique is a sensitive method for detecting pulmonary edema.