Potassium conductance activated during regulatory volume decrease
by mudpuppy red blood cells.
Bergeron, Lori J., Arturo J. Stever, and Douglas B. Light.
Department of Biology, Ripon College, Ripon, WI 54971
APStracts 2:0308R, 1995.
The cellular basis of regulatory volume decrease (RVD) by mudpuppy
(Necturus maculosus) red blood cells was examined. Volume regulation
was inhibited by replacing extracellular Na+ with K+. In contrast,
addition of gramicidin (5 [mu]M) to the extracellular medium enhanced
RVD. The K+ channel blocker quinine (1 mm) also inhibited RVD, and
this inhibition was reversed by gramicidin (5 [mu]M). In addition, a
0 Ca2+-EGTA Ringer's blocked RVD whereas the Ca2+ ionophore A23187 (2
[mu]M) enhanced recovery of cell volume. The stretch-activated ion
channel antagonist gadolinium (10 [mu]M) inhibited RVD, and this
effect was reversed by A23187 (2 [mu]M). Further, the calmodulin
inhibitors pimozide (10 [mu]M) and N-(6-aminohexyl)-5-chloro-1
-napthalenesulfonamide (W-7, 0.1 mM) blocked RVD, and this inhibition
was reversed with gramicidin (5 [mu]M). Consistent with these
findings, a K+-selective membrane conductance was activated by
exposing RBCs to a 0.5X Ringer's solution (observed with the whole
-cell patch clamp technique). This conductance was inhibited by
quinine (1 mM), gadolinium (10 [mu]M), and pimozide (10 [mu]M). These
results indicate that cell swelling activates a K+ conductance by a
Ca2+-calmodulin-dependent mechanism, and this channel mediates K+
loss during RVD.
Received 5 July 1995; accepted in final form 1 November 1995.
APS Manuscript Number R418-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 November 95