Determinants of the transmembrane distribution of chloride in rat lymphocytes: role of Cl(-)-HCO3- exchange

Abstract

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)

P2X7 Receptor-Dependent Cell Death Is Modulated during Murine T Cell Maturation and Mediated by Dual Signaling Pathways

“…11A). The reported value of intracellular Cl Ϫ concentration in lymphocytes is in the range of 50 -85 mM (39,40), and the extracellular Cl Ϫ concentration was ϳ108 mM under our experimental conditions, suggesting that extracellular Cl Ϫ influx also plays a significant role in the regulation of P2X 7 receptor-mediated splenic T cell shrinkage. In contrast, Auger et al (9) reported that the mode of P2X 7 receptor-mediated thymocyte death is necrosis/lysis via the phosphorylation of ERK1/2, rather than apoptosis.…”

Involvement of Chloride in Apoptotic Cell Death Induced by Activation of ATP-sensitive P2X7 Purinoceptor

“…The attempt to measure Cl Ϫ influx by using Cl Ϫ -sensitive fluorescent probe MQAE was unsuccessful because we were not able to distinguish the Cl Ϫ -dependent fluorescence change from the effect of leakage of MQAE (molecular weight 326) through the membrane pore formed in response to BzATP. The reported value of intracellular Cl Ϫ concentration in lymphocytes is in the range of 50 -85 mM (36,37), and the extracellular Cl Ϫ concentration is likely to be from 120 to 135 mM. Given the gradient of Cl Ϫ concentration across the membrane, opening a non-selective pore should result in Cl Ϫ moving into the cell.…”

Balance of Na+, K+, and Cl– Unidirectional Fluxes in Normal and Apoptotic U937 Cells Computed With All Main Types of Cotransporters

“…Therefore, the abbreviations NC and KC are used, but not NCC and KCC. It is known that unidirectional Na + –Cl – coupled cotransport with 1:1 stoichiometry may be performed both by a single transport protein, like thiazide-sensitive Na + –Cl – cotransporter ( Gamba, 2005 ), and by two functionally coupled exchangers, NHE and Cl – /HCO 3 – ( Garcia-Soto and Grinstein, 1990 ; Hoffmann et al, 2009 ). The genetically identified cotransporters NKCC1 (SLC12A2) and KCC1 (SLC12A4) are expressed in U937 cells 1 , 2 .…”