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Potassium transport of the frog retinal pigment epithelium: autoregulation of potassium activity in the subretinal space.
Author(s) -
la Cour M,
Lund-Andersen H,
Zeuthen T
Publication year - 1986
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1986.sp016128
Subject(s) - retinal pigment epithelium , retinal , biophysics , chemistry , retina , ouabain , permeability (electromagnetism) , membrane potential , epithelium , ion transporter , steady state (chemistry) , membrane , anatomy , biology , biochemistry , sodium , genetics , organic chemistry , neuroscience
The K+ transport of the isolated retinal pigment epithelium from the bull‐frog was studied using micropuncture with double‐barrelled ion‐selective micro‐electrodes. Transient changes of intracellular values of electrical potential and K+ activity were monitored in response to abrupt changes in the K+ concentration on the retinal side of the tissue. The data were interpreted in terms of a simple three‐compartment model of the epithelium in which the retinal (or apical) and choroidal (or basal) membranes separate the cellular compartment from the retinal and choroidal compartments. K+ transport across the retinal membrane was described by an active ouabain‐sensitive K+ influx in parallel with a passive electrodiffusive K+ efflux. In steady state under control conditions, the active K+ influx (pump rate) averaged 0.18 X 10(‐9) mol cm‐2 s‐1. The electrodiffusive K+ efflux was described by a K+ permeability, which in steady state under control conditions averaged 1.7 X 10(‐5) cm s‐1. K+ transport across the choroidal membrane was described as purely electrodiffusive. In steady state under control conditions, the K+ permeability of the choroidal membrane averaged 0.6 X 10(‐5) cm s‐1. When the K+ concentration on the retinal side of the tissue was increased from its control value, the K+ permeability of the retinal membrane decreased and the K+ permeability of the choroidal membrane increased. This caused the epithelium to attain a new steady state in which the cells transported K+ away from the retinal compartment at a high rate. When the K+ concentration on the retinal side of the tissue was decreased from its control value, the K+ permeability of the retinal membrane increased and the pump rate decreased. This caused the epithelial cells to transport K+ from the cellular compartment into the retinal compartment. In effect, the K+ transport of the retinal pigment epithelium depends on the K+ concentration in the retinal compartment in such a way as to keep variations in this concentration at a minimum.