Journal
AMERICAN JOURNAL OF PHYSIOLOGY-CELL PHYSIOLOGY
Volume 316, Issue 6, Pages C792-C804Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/ajpcell.00010.2019
Keywords
anion conductance; anion permeability; RPE
Categories
Funding
- National Institutes of Health [EY-08850, EY-07703]
- Research to Prevent Blindness
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Our recent electrophysiological analysis of mouse retinal pigment epithelial (RPE) cells revealed that in the presence of 10 mM external thiocyanate (SCN-), voltage steps generated large transient currents whose time-dependent decay most likely results from the accumulation or depletion of SCN- intracellularly. In the present study, we investigated the effects of more physiologically relevant concentrations of this biologically active anion. In whole cell recordings of C57BL/6J mouse RPE cells, we found that, over the range of 50 to 500 mu M SCN-, the amplitude of transient currents evoked by voltage steps was proportional to the extracellular SCN- concentration. Transient currents were also produced in RPE cells when the membrane potential was held constant and the external SCN- concentration was rapidly increased by pressure-ejecting 500 mu M SCN- from a second pipette. Other results indicate that the time dependence of currents produced by both approaches results from a change in driving force due to intracellular SCN- accumulation or depletion. Finally, by applying fluorescence imaging and voltage-clamping techniques to BALB/c mouse RPE cells loaded with the anion-sensitive dye MQAE, we demonstrated that in the presence of 200 or 500 mu M extracellular SCN-, depolarizing voltage steps increased the cytoplasmic SCN- concentration to an elevated steady state within several seconds. Collectively, these results indicate that, in the presence of physiological concentrations of SCN- outside the RPE, the conductance and permeability of the RPE cell membranes for SCN- are sufficiently large that SCN- rapidly approaches electrochemical equilibrium within the cytoplasm when the membrane voltage or external SCN- concentration is perturbed.
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