Anion exchange in type II pneumocytes freshly isolated from adult guinea-pig lung.

We have studied chloride influx and efflux in a highly purified preparation of type n cells freshly isolated from adult guinea-pig lung using Cl. Chloride uptake was time-dependent, saturable (K<10 mM) and was inhibited by 4,4′-diisothiocyanatostilbene-2,2′-disulphonic acid (DIDS; K≈80 μM). In the absence of external chloride (substituted by gluconate), Cl uptake exhibited an overshoot above equilibrium. The rate of Cl entry was strongly inhibited by addition of external nitrate; sulphate was a weaker inhibitor. Cl efflux was stimulated by external bromide > bicarbonate ≥ chloride ≥ citrate; and was inhibited by proprionate > acetate > oxalate. Although the 'chloride channel blocker' 4-nitro-2-(3-phenylpropylamino)benzoate (0.14 mM) caused an inhibition, Cl influx did not appear to be electrogenic. These data are compatible with the existence of a substantial electroneutral anionexchange pathway for chloride transport in freshly isolated adult type II pneumocytes. [ABSTRACT FROM AUTHOR]