Modulation of chloride secretion across the pigmented rabbit conjunctiva

Exp Eye Res. 1998 Mar;66(3):275-82. doi: 10.1006/exer.1997.0459.

Abstract

The purpose of the present study was to investigate whether active Cl- secretion in the pigmented rabbit conjunctiva was subject to cAMP, Ca2+ and protein kinase C (PKC) modulation. The excised pigmented rabbit conjunctivas were mounted in the modified Ussing-type chambers for measurement of unidirectional 36Cl fluxes under the open-circuit condition and of the short-circuit current (Isc), potential difference, and transconjunctival electrical resistance. The results indicate that Cl- secretion across the conjunctiva was abolished by mucosal application of 1 mM N-phenylanthranilic acid and was reduced by 40% by serosal application of 10 microM bumetanide. Net Cl- flux was stimulated by 133% by 1 mM 8-Br cAMP, 107% by 10 microM A23187, and 87% by 1 microM phorbol 12-myristate-13-acetate (PMA), suggesting that cAMP, Ca2+, and PKC all modulated active Cl- secretion, respectively. There existed a linear correlation between measured changes in net Cl- flux and observed changes in Isc (r2=0.99). The serial treatment of the conjunctiva with (a) 1 mM 8-Br cAMP and 10 microM A23187 and (b) 10 microM A23187 and 1 microM PMA resulted in sequence-independent, additive stimulation of Isc. In the case of 1 mM 8-Br cAMP and 1 microM PMA, additive stimulation of Isc was observed only when 1 mM 8-Br cAMP was added prior to 1 microM PMA. These results suggest that a given pharmacological agent may affect more than one channel type and that there might be a possible connection among the channels at the signal transduction level. In summary, Cl- appears to enter the pigmented rabbit conjunctiva from the serosal fluid via Na+-(K+)-2Cl- cotransport process and exit to the mucosal fluid via channels, resulting in active Cl- secretion. Active Cl- secretion in the pigmented rabbit conjunctiva appears to be modulated by cAMP, Ca2+, and PKC.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Calcimycin / pharmacology
  • Calcium / metabolism*
  • Chlorides / metabolism*
  • Conjunctiva / metabolism*
  • Cyclic AMP / metabolism*
  • Drug Combinations
  • Male
  • Protein Kinase C / metabolism*
  • Rabbits
  • Tetradecanoylphorbol Acetate / pharmacology

Substances

  • Chlorides
  • Drug Combinations
  • Calcimycin
  • Cyclic AMP
  • Protein Kinase C
  • Tetradecanoylphorbol Acetate
  • Calcium