REDUCTION AND ACCUMULATION OF METHYLENE-BLUE BY THE LUNG

We studied the disposition of methylene blue added to the perfusate pa ssing through isolated perfused rabbit lungs. Experiments were carried out in a recirculating or single-pass mode, the latter with either a steady infusion or bolus injection of the dye in its blue oxidized for m (MB(+)) or in its colorless reduced leukomethylene blue form (MBH). The recirculation experiments revealed that the dye was taken up by th e lungs and that a substantial fraction (similar to 16%) of the MB(+) entering the pulmonary artery was reduced before it emerged from the p ulmonary veins. Sequestration of the dye by the lungs was a relatively slow process, and the blue color of the lungs at a time when there wa s little dye left in the perfusate suggests that much of the sequester ed dye was in the oxidized form. The results from the single-pass bolu s and steady infusion experiments suggest that MBH diffuses rapidly be tween perfusate and tissue and that it is more soluble in the tissue t han in the perfusates used in the study. In this context, the concept of ''solubility'' includes the impact of the rapidly equilibrating ass ociations of the dye with the perfusate albumin and tissue components. The observed characteristics of the disposition of the methylene blue within the lungs and the rapid rate of its reduction on passage throu gh the lungs suggest that it may be useful to evaluate the possibility that changes in reduction, uptake, and/or sequestration rates may ref lect alterations in the metabolic function of the lungs.