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.