Distribution of chloride ion in intercellular space of retinal pigment epithelium--effects of various agents.

The distribution of chloride ion (Cl-) in the frog retinal pigment epithelium (RPE) was investigated histologically to determine the effects of various agents on the Cl- concentration in the intracellular spaces of the RPE. Fixation with osmium tetroxide containing silver acetate resulted in the deposit of silver chloride (AgCl) in the RPE, and this was confirmed by X-ray microanalysis. The Cl- concentration in the intercellular space decreased significantly after the fixation and washing with sucrose solution before Cl- deposition procedures, as well as after the 2,4-dinitrophenol treatment, which inhibits the active transport mechanism of the RPE. The intercellular Cl- concentration decreased after the cyclic AMP or cyclic GMP treatment which, respectively, decreases or might decrease Cl- transport from the apical to the basolateral side of the RPE. The Cl- concentration in the intercellular spaces did not change after the ouabain treatment. The results of the present study suggest that the changes in the Cl- concentration in the intercellular spaces of the RPE are related to the status of Cl- transport in the RPE.