The Journal of General Physiology, Vol 68, 281-296, Copyright © 1976 by The Rockefeller University Press
Intracellular Na+, K+, and C1- activities in Balanus photoreceptors
HM Brown
Ion-sensitive microelectrodes were used to measure intracellular activities
(aix) of Na+, K+, and C-1 in Balanus photoreceptors. Average values of
aiNa, aiK, and aiCl were 28 mM, 120 mM, and 65 mM, respectively.
Equilibrium potentials calculated from these average values were: Na+ +64
mV, K+ - 77 mV, and and Cl- -42 mV; ther average value of the resting
potential for all cells examined was -41 mV. Long exposure to intense
illumination produced measurable increases in aiNa. Classical Na+ - K+
reciprocal dilution experiments were analyzed with and without observed
changes in aiK. As aoK was increased, the membrane depolarized, and aiK
increased. Better agreement was found between the membrane potential and
the directly determined EK than expected from the standard relation between
Em and aoK. The latter produced pNa:pK estimates of the resting
photoreceptor membrane that were higher than estimates based on data from
the ion electrodes. Generally, Em was more negative than EK as aoK was
increased. This is consistent with a significant chloride permeability in
the dark-adapted photoreceptor.
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Facebook 
Reddit 
Technorati 
Twitter What's this?
