The present study demonstrates, for the first time, that the excised pigmented rabbit conjunctiva is a tight barrier capable of active Cl- transport. The transepithelial potential difference was 17.7 +/- 0.8 mV (tear-side negative), the short-circuit current was 14.5 +/- 0.7 microA/cm2, and the transconjunctival resistance was 1.3 +/- 0.1 k omega.cm2 for n = 45 tissues. Various inhibitors including ouabain (a Na+/K(+)-ATPase inhibitor), amiloride (a Na+ transport blocker), N-phenylanthranilic acid (a chloride transport inhibitor), bumetanide (an inhibitor of Na(+)-(K+)-Cl- cotransport process), and BaCl2 (a K+ channel blocker) were used on the mucosal and serosal sides of the tissue mounted in Ussing chambers to determine the involvement of the respective ion transport processes in the observed short-circuit current across the conjunctiva. The results suggest that a Cl- conductive pathway is present 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 conjunctiva.