Pharmacological modulation of fluid secretion in the pigmented rabbit conjunctiva

We determined net fluid secretion rate across the pigmented rabbit conjunct iva in the presence and absence of pharmacological agents known to affect a ctive Cf secretion and Na+ absorption. Fluid flow across a freshly excised pigmented rabbit conjunctiva mounted between two Lucite half chambers was m easured by a pair of capacitance probes in an enclosed cabinet maintained a t 37 degrees C and a relative humidity of 70%. Fluid transport was also mea sured in the presence of compounds known to affect active Cl- secretion (cA MP, UTP, and ouabain), Na+ absorption (D-glucose), or under the Cl--free co ndition on both sides of the tissue. Net fluid secretion rate across the pi gmented rabbit conjunctiva in the serosal-to-mucosal direction at baseline: was 4.3 +/- 0.2 mu l/hr/cm(2) (mean +/- s.e.m.). Net fluid secretion rate was increased approximately two-fold by mucosally applied 1 mM 8-Br cAMP (8 .4 +/- 0.4 mu l/hr/cm(2)) and 10 mu M UTP (9.8 +/- 0.6 mu l/hr/cm(2)), but was abolished by either serosally applied 0.5 mM ouabain (0.3 +/- 0.1 mu l/ hr/cm(2)) or under the Cl- free conditions (0.06 +/- 0.04 mu l/hr/cm(2)) Mu cosal addition of 20 mM D-glucose decreased net fluid secretion rate to 1.0 +/- 0.5 mu l/hr/cm(2). In conclusion, the pigmented rabbit conjunctiva app ears to secrete fluid secondary to active Cf secretion. This net fluid secr etion is subject to modulation by changes in active Cl- secretion rate and in mucosal fluid composition such as glucose concentration. (C) 2000 Elsevi er Science Inc.