Catecholamine-stimulated ion transport in duck red cells. Gradient effects in electrically neutral [Na + K + 2Cl] Co-transport.

Abstract

The transient increase in cation permeability observed in duck red cells incubated with norepinephrine has been shown to be a linked, bidirectional, co-transport of sodium plus potassium . This pathway, sensitive to loop diuretics such as furosemide, was found to have a [Na + K] stoichiometry of 1 :1 under all conditions tested . Net sodium efflux was inhibited by increasing external potassium, and net potassium efflux was inhibited by increasing external sodium . Thus, the movement of either cation is coupled to, and can be driven by, the gradient of its co-ion . There is no evidence of trans stimulation of cotransport by either cation . The system also has a specific anion requirement satisfied only by chloride or bromide . Shifting the membrane potential by varying either external chloride (at constant internal chloride) or external potassium (at constant internal potassium in the presence of valinomycin and DIDS [4,4'-diisothiocyano-2,2'-disulfonic acid stilbene]), has no effect on norepinephrine-stimulated net sodium transport . Thus, this co-transport system is unaffected by membrane potential and is therefore electrically neutral . Finally, under the latter conditions-when E,n was held constant near Ex and chloride was not at equilibrium-net sodium extrusion against a substantial electrochemical gradient could be produced by lowering external chloride at high internal concentrations, thereby demonstrating that the anion gradient can also drive co-transport . We conclude, therefore, that chloride participates directly in the co-transport of [Na + K + 2Cl] .

Acetylcholine‐evoked potassium release in the mouse pancreas.

“…This fits exactly the anion requirements of Na+-K+-2Cl-cotransport in red cells and cultured HeLa cells (Chipperfield, 1981;Aiton & Simmons, 1983) as well as the anion requirements of salivary fluid secretion (Lundberg, 1957) whereas with regard to the C1--HCO3-exchanger it has been known for a long time that NO3-is an equally good exchange partner for Cl-as Cl-itself while Br-and l-are less efficient (Gunn, Wieth & Tosteson, 1975). Our findings presented in Figs. 3-6 are therefore most easily interpreted by assuming the existence of linked Na+, K+ and Cl-movements through a Na+-K+-2Cl-co-transporter (Aiton, Chipperfield, Lamb, Ogden & Simmons, 1981;Dunham & Ellory, 1981;Chipperfield, 1980Chipperfield, ,1981Dunham, Stewart & Ellory, 1980;Greger & Schlatter, 1981,1984Haas, Schmidt & McManus, 1982;Hannafin, Kinne-Safran, Friedman & Kinne, 1983). The results in the mouse pancreas can most easily be explained by assuming that the Na+-K+-2Cl-co-transport moves the ions from the cell interior to the exterior (Singh, 1984a), i.e.…”

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].…”

“…7 B) against their respective values FIGURE 7. Net chemical driving force (AV.,et) in joules per mole as a function of (A) Na i and (B) MCV calculated according to Haas et al (1982) and Duhm and GGbel (1984). The values of the driving force were calculated using individual Na~, I~, and Clo concentrations (data not shown) and a constant chloride ratio (0.72), as well as the respective values of Nai and Ki indicated in Fig.…”

Volume-regulatory responses of Amphiuma red cells in anisotonic media. The effect of amiloride.

“…The ionic mechanism of the Amphiuma VRI response differs substantially from that of avian red cells. The avian response involves a furosemide-sensitive cotransport of Na, K, and Cl (Kregenow, 1978(Kregenow, , 1981Schmidt and McManus, 1977a, b;McManus and Schmidt, 1978 ;Palfrey and Greengard, 1981 ;Haas et al, 1982). A sufficient decrease in the medium concentration of any of these three ions prevents duck cells from enlarging (Kregenow, 1977(Kregenow, , 1978(Kregenow, , 1981Schmidt and McManus, 1977a, b; Kregenow and Caryk, 1979).…”