Effects of ph on the potassium current in rabbit corneal epithelial
cells.
Rich, Adam, Christopher Bartling, Gianrico Farrugia, and James L. Rae.
Departments of Physiology and Biophysics, Gastroenterology and
Ophthalmology, Mayo Foundation, Rochester, Minnesota 55905, (507)
-284-1118 or FAX (507)-284-8566
APStracts 3:0290C, 1996.
The effects of pH on a K+ conductance were measured using the
amphotericin perforated-patch whole cell voltage clamp technique in
freshly dispersed rabbit corneal epithelial cells. Bath perfusion
with pH 6.00 Ringer's solution following standard Ringer's solution
(pH = 7.35) increased an outward K+-selective current (IK) from
120+/-29 pA to 312+/-64 pA during a step depolarization to +50 mV,
and hyperpolarized the resting membrane potential (Em) from -52+/-5
mV to -62+/-3 mV (P 0.05, n=15). Increasing bath pH to 8.5 decreased
IK from 183+/-40 pA to 114+/-35 pA (P 0.05, n=6) and depolarized Em
from -63+/-6 mV to -53+/-5 mV (P 0.05, n=6). Intracellular
acidification, using the weak electrolyte (NH4)2SO4, also increased
IK from 83+/-15 pA to 183+/-20 pA (n=4, P=0.01) and hyperpolarized Em
from -51+/-8 mV to -68+/-6 mV (P=0.002). Intracellular alkalization
reduced IK 66+/-10 pA and depolarized Em to -36+/-8 mV (P=0.009).
Single channel studies in perforated outside-out vesicles showed that
a decrease in bath pH from 7.35 to 6.00 was accompanied by an
increase in the single channel open probability (NPo) from 0.43 to
0.64 at a membrane potential of 15 mV. NPo was also increased in
cell-attached patches. The unitary conductance, measured from -100 mV
to +100 mV, was not changed. These results indicate that pH modulates
the outward K+ current in rabbit corneal epithelial cells by changes
in NPo. (supported by grants EYO3282, EYO6005, and DKO8677-03)
Received 29 March 1996; accepted in final form 6 September 1996.
APS Manuscript Number C178-6.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 7 October 1996