ACTIVE CHLORIDE TRANSPORT IN THE PIGMENTED RABBIT CONJUNCTIVA

The present study demonstrates, for the first time, that the excised p igmented rabbit conjunctiva is a tight barrier capable of active Cl- t ransport. The transepithelial potential difference was 17.7 +/- 0.8 mV (tear-side negative), the short-circuit current was 14.5 +/- 0.7 mu A /cm(2), and the transconjunctival resistance was 1.3 +/- 0.1 k Omega.c m(2) for n = 45 tissues. Various inhibitors including ouabain (a Na+/K +-ATPase inhibitor), amiloride (a Na+ transport blocker), N-phenylanth ranilic acid (a chloride transport inhibitor), bumetanide (an inhibito r of Na+-(K+)-Cl(-)cotransport process), and BaCl2 (a K+ channel block er) were used on the mucosal and serosal sides of the tissue mounted i n Ussing chambers to determine the involvement of the respective ion t ransport processes in the observed short-circuit current across the co njunctiva. The results suggest that a Cl- conductive pathway is presen t on the mucosal side of the conjunctiva, whereas Na+/K+-ATPase, Na+-( K+)-Cl- cotransport process, and K+ conductive pathways are present on its serosal side. Amiloride-sensitive Na+-conductive pathways do not appear to be present on either side of the pigmented rabbit conjunctiv a.