The dependence on external cation of sodium and potassium fluxes across the human red cell membrane at low temperatures.

Abstract

SUMMARY1. The fluxes of Na and K across the human red cell membrane have been studied as functions of temperature and external cation composition.2. In media containing any of a variety of organic compounds as the principal cation (choline, N-methyl-D-glucamine (NMDG), arginine, L-lysine and trimethylphenylammonium), the ouabain plus bumetanide-insensitive influxes and effluxes of Na and K displayed marked paradoxical temperature dependence such that the flux minimum, which normally occurs at about 8-10 0C in a NaCl medium, was shifted up to about 20 'C.3. Inhibitor and anion replacement studies excluded contributions by the major carrier-mediated systems evident at 37 'C.4. At 0 'C in NMDG, about 1 mM-external Na and 10 mM-external K were required half-maximally to inhibit the K and Na influxes respectively. 5. When the K(86Rb) efflux in NMDG media at 0 'C was measured in the presence of low concentrations of a series of external inorganic ions and guanidine, the order of potency for reduction of the efflux was Li > Mg = Ca > Ba > Sr > Na > Rb = Cs = guanidine > K.6. The influxes of the neutral amino acid L-leucine and the cationic species L-lysine both showed simple monotonic temperature dependence in Na and NMDG media.7. These effects show that the permeability of the human red cell membrane to inorganic univalent cations at low temperatures is markedly dependent on the external ionic conditions. Low permeability is favoured by the presence of cations with a high charge density.

Effects of low ionic strength media on passive human red cell monovalent cation transport.

“…A. C. HALL AND J. C. ELLORY compares K+ influx in sucrose medium with that in physiological NaCl medium as a function of temperature. In addition, data on the effect of 1 mM-LiCl in sucrose medium are given, since it has been shown that Li' is a potent inhibitor of the paradoxical temperature effect (Blackstock & Stewart, 1986). In NaCl medium the K+ influx does not vary greatly with temperature over the range of 0-25°C, although the flux at 0°C is higher than at 8°C in accordance with previous results ).…”

“…However at 37°C, Li+ had no effect on the low ionic strength-stimulated flux. We therefore conclude that the flux in a solution of low ionic strength at low temperature can be resolved into two independent components: (i) a low temperature-induced component which is Li+ sensitive (Blackstock & Stewart, 1986) and (ii) a low ionic strength-induced component which is not Li+ sensitive.…”

“…Firstly, Stewart et al (1980) and Blackstock & Stewart (1986) have shown that low temperature induces a cation flux which increases when temperature is lowered (below 8°C) with properties reminiscent of the low ionic strength effect. There is therefore the possibility that the present low ionic strength effect and the temperature effect are manifestations of the same phenomenon.…”

“…In this respect measurements of K+ flux in high and low ionic strength media under high hydrostatic pressure, and at low temperature, were performed (e.g. see Blackstock & Stewart, 1986;Hall & Ellory, 1986a).…”

Two British families with variants of the ‘cryohydrocytosis’ form of hereditary stomatocytosis

“…The temperature dependence of this passive leak flux in normal cells is complex and shows a minimum at about 8°C (Stewart et al , 1980). The temperature of this minimum can be increased up to about 23°C by replacement of either Na or Cl in the bathing medium by organic cations or anions (Wieth, 1970; Blackstock & Stewart, 1986).…”