Modes of operation of an electroneutral na+/li+ countertransport in
human skin fibroblasts.
Zerbini, Gianpaolo, Ruggero Mangili, Daniela Gabellini, and Guido
Pozza.
Renal Pathophysiology Laboratory, Division of Medicine, Scientific
Institute San Raffaele, University of Milan, Milan, Italy, I
-20132
APStracts 3:0389C, 1996.
An elevated activity of erythrocyte Na+-Li+ countertransport (SLC) is
an intermediate phenotype of human essential hypertension, but cells
other than erythrocytes have not been studied. Therefore, we have
examined several transport modes of Na+ for Li+ exchange in human
skin fibroblasts. External Na+-stimulated Li+ efflux had value of
152+/-31 nmol x mgprotein-1 x min-1, mean+/-SEM, (n=8). At pHi 7.3,
measurements of intracellular Na+-stimulated Li+ influx,
intracellular Li+-stimulated Na+ influx, and external Li+-stimulated
Na+ efflux gave very similar values indicating the presence of a
tightly coupled 1:1 Na+ for Li+ countertransport. This pathway was
not affected by DMA and changes in the membrane potential but
phloretin and intracellular acidification (pHi 6.8) were markedly
inhibitory. Kinetic analyses of the external Na+ site also compared
with SLC, although the internal site appeared to show a low affinity
for Li+. We conclude that a Na+/Li+ countertransport pathway similar
to that present in human RBC is expressed in human skin fibroblasts.
Received 24 June 1996; accepted in final form 13 November 1996.
APS Manuscript Number C358-6.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996