Ouabain-insensitive salt and water movements in duck red cells. III. The role of chloride in the volume response.

Abstract

A B S T a A C T This paper describes the effect of external chloride on the typical swelling response induced in duck red cells by hypertonicity or norepinephrine. Lowering chloride inhibits swelling and produces concomitant changes in net movements of sodium and potassium in ouabain-treated cells, which resemble the effect of lowering external sodium or potassium. Inhibition is the same whether chloride is replaced with gluconate or with an osmotic equivalent of sucrose. Since changes in external chloride also cause predictable changes in cell chloride, pH, and water, these variables were systematically investigated by varying external pH along with chloride. Lowering pH to 6.60 does not abolish the response if external chloride levels are normal, although the cells are initially swollen due to the increased acidity. Cells deliberately preswollen in hypotonic solutions with appropriate ionic composition can also respond to norepinephrine by further swelling. These results rule out initial values of cell water, chloride, and pH as significant variables affecting the response. Initial values of the chloride equilibrium potential do have a marked effect on the direction and rate of net water movement. If chloride is lowered by replacement with the permeant anion, acetate, Ec~ is unchanged and a normal response to norepinephrine, which is inhibited by furosemide, is observed. Increasing internal sodium by the nystatin technique also inhibits the response. A theory is developed which predicts that the cotransport carrier proposed in the previous paper (W. F. Schmidt and T.J. McManus. 1977b.J. Gen. Physiol. 70:81-97) moves in response to the net electrochemical potential difference driving sodium and potassium across the membrane. Predictions of this theory fit the data for both cations and anions.

Effect of Incubation Medium Electrolyte Concentration on Lens Volume

“…The loss of cell solute during volume equilibration in hypotonic medium is comparable to the gain in cell solute during volume equilibration in hypertonic medium. The latter process has been studied by Schmidt and McManus [21] in avian red blood cells and their findings are consistent with those reported in this paper. They note that the water uptake following hypertonic shrinking, which reflects changes in cellular electrolyte content, is three times more sensitive to the chloride concentration in the medium than it is to the concentration of sodium.…”

Internal magnesium, 2,3-diphosphoglycerate, and the regulation of the steady-state volume of human red blood cells by the Na/K/2Cl cotransport system.

“…1 A; Tosteson and Hoffman, 1960;Funder and Wieth, 1966b;Lee et al, 1984). Therefore, for cells in the steady state, where the sum Nai + Ki is constant with time, it is possible to calculate the net driving force, A~net , for cotransport from the chemical potential gradients of Na,K, and C1 that exist across the cell membrane, using the formula: as previously proposed (Schmidt and McManus, 1977; see also Haas et al, 1982, andG6bel, 1984). The calculation assumes a cotransport stoichiometry of 1 Na/1K/2CI as found for human red cells by Garay et a].…”

“…This is in light of the fact that the cotransport system is known to promote coupled, bidirectional net movements of Na, K, and CI in response to perturbations in cell volume (Kregenow, 1981;Siebens, 1985;Hoffmann and Simonsen, 1989) and/or changes in the net chemical potential driving forces (Schmidt and McManus, 1977;Duhm and Grbel, 1984). It has been reported by others (Adragna et al, 1982;Duhm and Grbel, 1982;Stewart, 1988) that there was a significant interindividual variability in the size of the cotransport flux, and that this flux also varied inversely with both the mean red cell volume (MCV) and K content (Duhm and Grbel, 1984).…”

Membrane Mechanisms in Volume Regulation in Vertebrate Cells and Epithelia

“…Careful kinetic studies confirmed the coupled influx of Na + and K + after cell shrinkage [284], and net flux measurements under a variety of conditions indicated a Na + : K + stoichiometry of 1: 1 [285]. Norepinephrine and other catecholamines mimick the RVI response and produce a cell swelling in isotonic medium when the external K + concentration is elevated [122,123,166,268,285,286]. The activation by norepinephrine seems to be mediated by changes in intracellular cAMP, and any agent that raises cAMP activates the cotransport system [14,168,247,248,268,277].…”