Modulation of water and urea transport in human red cells: Effects of pH and phloretin

1987 ◽  
Vol 99 (3) ◽  
pp. 157-164 ◽  
Author(s):  
Michael R. Toon ◽  
A. K. Solomon
Keyword(s):  
Red Cells ◽  
Urea Transport ◽  
Effects Of Ph ◽  
Human Red Cells

scholarly journals Urea permeability of human red cells.

1983 ◽  
Vol 82 (1) ◽  
pp. 1-23 ◽  
Author(s):  
J Brahm
Keyword(s):  
Permeability Coefficient ◽  
Red Cells ◽  
Urea Transport ◽  
Hydrophobic Core ◽  
Flow Tube ◽  
Maximal Inhibition ◽  
Simple Diffusion ◽  
Urea Permeability ◽  
Exchange Flux ◽  
Human Red Cells

The rate of unidirectional [14C]urea efflux from human red cells was determined in the self-exchange and net efflux modes with the continuous flow tube method. Self-exchange flux was saturable and followed simple Michaelis-Menten kinetics. At 38 degrees C the maximal self-exchange flux was 1.3 X 10(-7) mol cm-2 s-1, and the urea concentration for half-maximal flux, K1/2, was 396 mM. At 25 degrees C the maximal self-exchange flux decreased to 8.2 X 10(-8) mol cm-2 s-1, and K1/2 to 334 mM. The concentration-dependent urea permeability coefficient was 3 X 10(-4) cm s-1 at 1 mM and 8 X 10(-5) cm s-1 at 800 mM (25 degrees C). The latter value is consonant with previous volumetric determinations of urea permeability. Urea transport was inhibited competitively by thiourea; the half-inhibition constant, Ki, was 17 mM at 38 degrees C and 13 mM at 25 degrees C. Treatment with 1 mM p-chloromercuribenzosulfonate inhibited urea permeability by 92%. Phloretin reduced urea permeability further (greater than 97%) to a "ground" permeability of approximately 10(-6) cm s-1 (25 degrees C). This residual permeability is probably due to urea permeating the hydrophobic core of the membrane by simple diffusion. The apparent activation energy, EA, of urea transport after maximal inhibition was 59 kJ mol-1, whereas in control cells EA was 34 kJ mol-1 at 1 M and 12 kJ mol-1 at 1 mM urea. In net efflux experiments with no extracellular urea, the permeability coefficient remained constantly high, independent of a variation of intracellular urea between 1 and 500 mM, which indicates that the urea transport system is asymmetric. It is concluded that urea permeability above the ground permeability is due to facilitate diffusion and not to diffusion through nonspecific leak pathways as suggested previously.

In Vitro Assay of Platelet Adhesiveness with Washed and Tanned Human Red Cells

1968 ◽  
Vol 20 (03/04) ◽  
pp. 384-396 ◽  
Author(s):  
G Zbinden ◽  
S Tomlin
Keyword(s):  
Platelet Adhesion ◽  
Sodium Citrate ◽  
Blood Platelets ◽  
In Vitro Assay ◽  
Red Cells ◽  
Platelet Adhesiveness ◽  
Vitro Assay ◽  
In Vitro System ◽  
Human Red Cells

SummaryAn in vitro system is described in which adhesion of blood platelets to washed and tannic acid-treated red cells was assayed quantitatively by microscopic observation. ADP, epinephrine and TAME produced a reversible increase in platelet adhesiveness which was antagonized by AMP. With Evans blue, polyanetholsulfonate, phthalanilide NSC 38280, thrombin and heparin at concentrations above 1-4 u/ml the increase was irreversible. The ADP-induced increase in adhesiveness was inhibited by sodium citrate, EDTA, AMP, ATP and N-ethylmaleimide. EDTA, AMP and the SH-blocker N-ethylmaleimide also reduced spontaneous platelet adhesion to red cells. No significant effects were observed with adenosine, phenprocoumon, 5-HT, phthalanilide NSC 57155, various estrogens, progestogens and fatty acids, acetylsalicylic acid and similarly acting agents, hydroxylamine, glucose and KCN. The method may be useful for the screening of thrombogenic and antithrombotic properties of drugs.

Metabolic control of the K+ channel of human red cells

1990 ◽  
Vol 116 (1) ◽  
pp. 19-29 ◽  
Author(s):  
Pedro J. Romero ◽  
Carlos E. Ortíz ◽  
Carmelo Melitto
Keyword(s):  
Metabolic Control ◽  
Red Cells ◽  
K Channel ◽  
Human Red Cells

Interactions between sphered human red cells in tube flow: Technique for measuring the strength of antigen-antibody bonds

1982 ◽  
Vol 23 (2) ◽  
pp. 231-238 ◽  
Author(s):  
Harry L. Goldsmith ◽  
Phil Gold ◽  
Joseph Shuster ◽  
Koichi Takamura
Keyword(s):  
Red Cells ◽  
Tube Flow ◽  
Antigen Antibody ◽  
Human Red Cells

The distribution of intracellular calcium chelator (fura-2) in a population of intact human red cells

1993 ◽  
Vol 1148 (1) ◽  
pp. 152-156 ◽  
Author(s):  
Virgilio L. Lew ◽  
Zipora Etzion ◽  
Robert M. Bookchin ◽  
Rui daCosta ◽  
Heikki Väänänen ◽  
...  
Keyword(s):  
Intracellular Calcium ◽  
Red Cells ◽  
Fura 2 ◽  
Human Red Cells

scholarly journals HUMAN T CELLS BIND AUTOLOGOUS AND HOMOLOGOUS HUMAN RED CELLS

1974 ◽  
Vol 8 (4) ◽  
pp. 402-402
Author(s):  
Joseph Kaplan ◽  
C S Stulberg
Keyword(s):  
T Cells ◽  
Red Cells ◽  
Human T Cells ◽  
Human Red Cells

Caffeine activates a mechanosensitive Ca2+ channel in human red cells

Cell Calcium ◽  
2002 ◽  
Vol 31 (5) ◽  
pp. 189-200 ◽  
Author(s):  
J.F Cordero ◽  
P.J Romero
Keyword(s):  
Red Cells ◽  
Human Red Cells
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