Nitric oxide alters cytosolic potassium in cultured glomerular
mesangial cells.
Ganz, Michael B., Scott E. Kasner & Robert J. Unwin.
Department of Medicine, Nephrology Section, Cleveland V.A.Medical
Center-Case Western Reserve University, Cleveland, Ohio, Institute of
Urology and Nephrology, University Hospital, Middlesex Hospital,
London, W1N UK
APStracts 2:0012F, 1995.
Endothelium-derived relaxing factor (EDRF) is believed to be nitric
oxide (NO). Evidence suggests that it has important functions in the
regulation of mesangial cell (MC) tone and possibly in inflammation.
As a vasodilator, its vasorelaxant effect depends, in part, on
changes in cell membrane potential. We therefore tested the
hypothesis that MCs in culture produce NO that results in cell
relaxation through the opening of potassium conductance pathways. The
potassium-sensitive fluorescent dye, PBFI was used to detect rapid
changes in intracellular potassium ([K+]i). The membrane
potential dye, Di-4-ANEPPS was used to detect changes in membrane
potential. Basal [K+]i was 92 +/- 9 nM (n=46). In response to
sodium nitroprusside (SNP), acetylcholine (ACh) and bradykinin (BK),
[K+]i decreased to 72 +/- 7 nM (n=5, P<0.05), 70 +/- 8 nM (n=7,
P<0.05), and [K+]i to 69 +/- 13 nM (n=6, P<0.05), respectively.
[K+]i rapidly returned to basal level in the continued presence
of all three agonists. The SNP-, ACh- and BK-induced decrease in
[K+]i was significantly blunted by barium by 85%, 92%, and 89%,
respectively (n>4 for each agonists examined P<0.0001). L-NMMA and
methylene blue, inhibited the [K+]i lowering effect of ACh and
BK, 94 and 85% (n=5 for each agonist, P<0.0001) for L-NMMA, and 67
and 72% (n=5 for each agonist, P<0.001) for methylene blue. ACh and
BK induced a transient hyperpolarization; Di-4-ANEPPS ratio decreased
from 1.43 +/- 0.05 to 1.30 +/- 0.05 for ACh (n=5, P<0.01) and 1.38 +/- 0.03
to 1.29 +/- 0.04 (n=5, P<0.01). The hyperpolarization effect was
blunted by L-NMMA for both ACh and BK. These results suggest that MCs
in culture may possess the constitutive form of NO synthase and
respond to NO. The NO, in turn, might affect MC function through
changes in cell potassium flux and thereby influence glomerular
filtration.
Received 26 October 1994; accepted in final form 27 December
1994.
APS Manuscript Number F389-4.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 February 1995.