Temperature dependence of anion transport inhibitor binding to human red cell membranes

1985 ◽  
Vol 23 (1-2) ◽  
pp. 139-145 ◽  
Author(s):  
Richard G. Posner ◽  
James A. Dix
1973 ◽  
Vol 61 (6) ◽  
pp. 727-746 ◽  
Author(s):  
W. R. Galey ◽  
J. D. Owen ◽  
A. K. Solomon

The temperature dependence of permeation across human red cell membranes has been determined for a series of hydrophilic and lipophilic solutes, including urea and two methyl substituted derivatives, all the straight-chain amides from formamide through valeramide and the two isomers, isobutyramide and isovaleramide. The temperature coefficient for permeation by all the hydrophilic solutes is 12 kcal mol-1 or less, whereas that for all the lipophilic solutes is 19 kcal mol-1 or greater. This difference is consonant with the view that hydrophilic molecules cross the membrane by a path different from that taken by the lipophilic ones. The thermodynamic parameters associated with lipophile permeation have been studied in detail. ΔG is negative for adsorption of lipophilic amides onto an oil-water interface, whereas it is positive for transfer of the polar head from the aqueous medium to bulk lipid solvent. Application of absolute reaction rate theory makes it possible to make a clear distinction between diffusion across the water-red cell membrane interface and diffusion within the membrane. Diffusion coefficients and apparent activation enthalpies and entropies have been computed for each process. Transfer of the polar head from the solvent into the interface is characterized by ΔG‡ = 0 kcal mol-1 and ΔS‡ negative, whereas both of these parameters have large positive values for diffusion within the membrane. Diffusion within the membrane is similar to what is expected for diffusion through a highly associated viscous fluid.


Blood ◽  
1967 ◽  
Vol 30 (6) ◽  
pp. 785-791 ◽  
Author(s):  
RONALD S. WEINSTEIN ◽  
ROGER A. WILLIAMS

Abstract Electron microscopic studies on dried isolated red cell ghosts have been reported to show lesions associated with cell membranes in paroxysmal nocturnal hemoglobinuria (PNH). In this study, carbon-platinum replicas of membranes of freeze-cleaved, partially hydrated PNH red cells and isolated PNH cell ghosts failed to confirm the existence of these abnormalities. This suggests that the previously described lesions are the products of drying artifacts, although they may reflect hidden structural differences between PNH and normal red cell membranes.


1985 ◽  
Vol 85 (1) ◽  
pp. 123-136 ◽  
Author(s):  
J H Kaplan ◽  
L J Kenney

Phosphorylation of red cell membranes at ambient temperatures with micromolar [32P]ATP in the presence of Na ions produced phosphoenzyme that was dephosphorylated rapidly upon the addition of ADP or K ions. However, as first observed by Blostein (1968, J. Biol. Chem., 243:1957), the phosphoenzyme formed at 0 degrees C under otherwise identical conditions was insensitive to the addition of K ions but was dephosphorylated rapidly by ADP. This suggested that the conformational transition from ADP-sensitive, K-insensitive Na pump phosphoenzyme (E1 approximately P) to K-sensitive, ADP-insensitive phosphoenzyme (E2P) is blocked at 0 degrees C. Since the ATP:ADP exchange reaction is a partial reaction of the overall enzyme cycle dependent upon the steady state level of E1 approximately P that is regulated by [Na], we examined the effects of temperature on the curve relating [Na] to ouabain-sensitive ATP:ADP exchange. The characteristic triphasic curve seen at higher temperatures when [Na] was between 0.5 and 100 mM was not obtained at 0 degrees C. Simple saturation was observed instead with a K0.5 for Na of approximately 1 mM. The effect of increasing temperature on the ATP:ADP exchange at fixed (150 mM) Na was compared with the effect of increasing temperature on (Na + K)-ATPase activity of the same membrane preparation. It was observed that (a) at 0 degrees C, there was significant ouabain-sensitive ATP:ADP exchange activity, (b) at 0 degrees C, ouabain-sensitive (Na + K)-ATPase activity was virtually absent, and (c) in the temperature range 5-37 degrees C, there was an approximately 300-fold increase in (Na + K)-ATPase activity with only a 9-fold increase in the ATP:ADP exchange. These observations are in keeping with the suggestion that the E1 approximately P----E2P transition of the Na pump in human red cell membranes is blocked at 0 degrees C. Previous work has shown that the inhibitory effect of Na ions and the low-affinity stimulation by Na of the rate of ATP:ADP exchange occur at the extracellular surface of the Na pump. The absence of both of these effects at 0 degrees C, where E1 approximately P is maximal, supports the idea that external Na acts through sites on the E2P form of the phosphoenzyme.


1987 ◽  
Vol 22 (3) ◽  
pp. 369-369
Author(s):  
R Simsolo ◽  
M Gimenez ◽  
B Grunfold ◽  
A Furci ◽  
L Da Graccn ◽  
...  

1978 ◽  
Vol 8 (3) ◽  
pp. 325-335 ◽  
Author(s):  
Ronald S. Weinstein ◽  
Jena K. Khodadad ◽  
Theodore L. Steck

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