Potassium-induced chloride secretion across the frog retinal pigment epithelium.
In the intact eye, a transition from light to dark increases K concentration ([K]o) from approximately 2 to 5 mM in the extracellular (subretinal) space between the photoreceptors and the retinal pigment epithelium (RPE) apical membrane. In control (HCO3/CO2) Ringer solution, 36Cl was actively absorbed across isolated bullfrog RPE (retina to choroid) at a rate of 0.31 +/- 0.02 (SE) mu eq.cm-2.h-1 (n = 15). Elevating apical [K]o from 2 to 5 mM reversed active 36Cl transport to secretion (choroid to retina), with a rate of 0.76 +/- 0.17 mu eq.cm-2.h-1. This reversal was completely inhibited by 1 mM 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) in either the apical or basal bath. In open circuit, elevating [K]o induced a similar reversal of net 36Cl flux and inhibited fluid absorption by approximately 25%. Apical Ba2+ (1 mM), decreased CO2 (5 to 1%), or increased apical bath HCO3 concentration ([HCO3]o) also caused a DIDS-inhibitable reversal of active 36Cl flux. A 10-fold reduction of apical bath Na or [HCO3]o significantly inhibited [K]o, Ba2+, and low CO2-induced Cl secretion. All of these results can be understood in terms of an intracellular pH-dependent stimulation of the basolateral membrane Cl-HCO3 exchanger.
Edelman
J L
JL
School of Optometry, University of California, Berkeley 94720.
Lin
H
H
Miller
S S
SS
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000468:Alkalies / Q000378:metabolism; D000818:Animals; D001639:Bicarbonates / Q000494:pharmacology; D001693:Biological Transport, Active; D002712:Chlorides / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009994:Osmolar Concentration; D010857:Pigment Epithelium of Eye / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism / Q000494:pharmacology*; D011892:Rana catesbeiana; D012964:Sodium / Q000494:pharmacology
D000468:Alkalies; D001639:Bicarbonates; D002712:Chlorides; D012964:Sodium; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D011188:Potassium