PROTECTION OF PERFUSED LUNG FROM OXIDANT INJURY BY INHIBITORS OF ANION-EXCHANGE

Hyperoxic lung injury is enhanced in isolated perfused lungs (IPL) in the presence of L-arginine. Reactive O-2 species such as superoxide an ion (O-2(-).) produced during hyperoxia are known to react with nitric oxide to form the strong oxidant species peroxynitrite. The appearanc e df O; in red blood cell membranes in vitro and in buffer-perfused lu ng preparations can be inhibited by the stilbene compound 4,4'-diisoth iocyanostilbene-2,2 '-disulfonic acid (DIDS). DIDS also inhibits anion exchange across the cell membrane regulated by a family of anion exch ange proteins (AE). In this study, we hypothesized that anion exchange inhibitors would prevent lung injury from hyperoxia and L-arginine (O -2 + L-Arg) by decreasing O-2(-). flux into the vascular space of the IPL. WE found that both DIDS and a structurally distinct anion transpo rt blocker, dipyridamole, protected the rabbit IPL from pulmonary hype rtension and edema produced by O-2 + L-Arg. The protective effect was associated with increased nitrite concentrations in the perfusate. Pro tection also was conferred when sodium bicarbonate in the perfusion bu ffer was replaced with either sodium thiosulfate or N-2-hydroxyethylpi perazine-N'-2-ethanesul-fonic acid (HEPES). In lungs perfused with thi osulfate or HEPES-containing buffer, protection from O-2 and L-arginin e was also associated with diminished detection of reducing activity c onsistent with O-2(-). in the vascular space. Western blot analysis of lung protein and immunocytochemical staining of lung sections using a ntibodies against rabbit red blood cell AE1 and mouse gastric AE2 pept ide showed that lung contains membrane protein antigenically similar t o gastric AE2. These data suggest the possibility that inhibition of A E or other anion transporters may play an important role in mediating oxidative lung injury.