pHi-dependent Cl-HCO3 exchange at the basolateral membrane of frog retinal pigment epithelium.
Intracellular pH (pHi) measurements in frog retinal pigment epithelium using the pH-sensitive dye 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein demonstrate that the basolateral membrane contains a pHi-sensitive Cl-HCO3 exchanger. In control Ringer solution, the removal of Cl from the basal bath alkalinized the cells by 0.07 +/- 0.03 (SD) pH units (n = 39) with an initial rate of 0.022 +/- 0.0013 pH units/min. This effect was blocked by 0.5 mM basal 4,4'-diisothiocyanostilbene-2,2'- disulfonic acid or the removal of HCO3 from both the apical and basal baths. The rate of the exchange is reduced by acidification and increased by alkalinization. Increasing apical bath K concentration ([K]o) from 2 to 5 mM approximates the [K]o change in the subretinal space of the intact eye following a transition from light to dark. This [K]o change alkalinized the cells by increasing the rate of the apical membrane Na-HCO3 cotransporter. In 5 mM apical [K]o, the initial rate of the 0 Cl-induced alkalinization was significantly increased to 304 +/- 13% (n = 4) of control (2 mM [K]o). These mechanisms regulate pHi and could also buffer changes in subretinal pH.
Lin
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School of Optometry, University of California, Berkeley 94720.
Miller
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SS
D000818:Animals; D017920:Antiporters / Q000378:metabolism*; D001639:Bicarbonates / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D027963:Chloride-Bicarbonate Antiporters; D005260:Female; D006863:Hydrogen-Ion Concentration; D007425:Intracellular Membranes / Q000378:metabolism; D007477:Ions; D008297:Male; D010857:Pigment Epithelium of Eye / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D011892:Rana catesbeiana; D012964:Sodium / Q000502:physiology
D017920:Antiporters; D001639:Bicarbonates; D027963:Chloride-Bicarbonate Antiporters; D007477:Ions; D012964:Sodium; D011188:Potassium