AJP - Cell Physiology, Vol 258, Issue 6 C1108-C1116, Copyright © 1990 by American Physiological Society
Determinants of the transmembrane distribution of chloride in rat lymphocytes: role of Cl(-)-HCO3- exchange
J. J. Garcia-Soto and S. Grinstein
Instituto de Investigacion en Biologia Experimental, Facultat de Quimica, Universidad de Guanajuato, Mexico.
The purpose of the present experiments was to establish the factors that
determine the intracellular Cl- concentration ([Cl-]i) of lymphocytes.
Coulometric and isotope equilibration determinations indicated that [Cl-]i
was in the range of 70-85 mmol/l cells. Since the membrane potential (Em)
of these cells approximates -55 mV, [Cl-]i is severalfold higher than the
level expected at electrochemical equilibrium (approximately 16 mM). This
suggests that conductive pathways contribute marginally to the distribution
of Cl-. Accordingly, altering the force driving conductive Cl- fluxes by
manipulating Em had little effect on [Cl-]i. The possible role of
electroneutral cation-Cl- cotransport in the accumulation of intracellular
Cl- was also assessed. 36Cl- uptake was largely unaffected by omission of
extracellular Na+ and K+ or by addition of bumetanide, a potent cotransport
inhibitor. Moreover, [Cl-]i remained unaltered for at least 1 h in cells
incubated without Na+ or K+ or in the presence of loop diuretics. Thus it
appears unlikely that Cl(-)-anion cotransport plays a major role in
maintaining [Cl-]i. A vigorous stilbene disulfonate-sensitive anion
exchanger was detected in thymocytes. This system constitutes a large
fraction of the Cl- flux pathways and is possibly a major contributor to
the establishment of [Cl-]i. Accordingly, modifying the force driving Cl-
through the exchanger, by altering pH at constant PCO2, resulted in changes
in cellular Cl- content and associated changes in cell volume. These
effects were markedly reduced in the nominal absence of HCO3- or in the
presence of disulfonic stilbene derivatives, suggesting that they are
mediated by Cl(-)-HCO3- exchange.(ABSTRACT TRUNCATED AT 250 WORDS)
