Reflection coefficient and permeability of urea and ethylene glycol in the human red cell membrane
The reflection coefficient (sigma) and permeability (P) of urea and ethylene glycol were determined by fitting the equations of Kedem and Katchalsky (1958) to the change in light scattering produced by adding a permeable solute to a red cell suspension. The measurements incorporated three important modifications: (a) the injection artifact was eliminated by using echinocyte cells; (b) the use of an additional adjustable parameter (Km), the effective dissociation constant at the inner side of the membrane; (c) the light scattering is not directly proportional to cell volume (as is usually assumed) because refractive index and scattering properties of the cell depend on the intracellular permeable solute concentration. This necessitates calibrating for known changes in refractive index (by the addition of dextran) and cell volume (by varying the NaCl concentration). The best fit was for sigma . 0.95, Po . 8.3 X 10(-4) cm/s, and Km . 100 mM for urea and sigma . 1.0, Po . 3.9 X 10(-4) cm/s, and Km . 30 mM for ethylene glycol. The effects of the inhibitors copper, phloretin, p-chloromercuriphenylsulfonate, and 5,5'-dithiobis (2-nitro) benzoic acid on the urea, ethylene glycol, and water permeability were determined. The results suggest that there are three separate, independent transport systems: one for water, one for urea and related compounds, and one for ethylene glycol and glycerol.
- Research Organization:
- Department of Physiology, University of Minnesota, Minneapolis
- OSTI ID:
- 5894850
- Journal Information:
- J. Gen. Physiol.; (United States), Vol. 81:2
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GLYCOLS
MEMBRANE TRANSPORT
UREA
WATER
CELL MEMBRANES
ERYTHROCYTES
PERMEABILITY
ALCOHOLS
AMIDES
BIOLOGICAL MATERIALS
BLOOD
BLOOD CELLS
BODY FLUIDS
CARBONIC ACID DERIVATIVES
CELL CONSTITUENTS
HYDROGEN COMPOUNDS
HYDROXY COMPOUNDS
MATERIALS
MEMBRANES
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXYGEN COMPOUNDS
560301* - Chemicals Metabolism & Toxicology- Cells- (-1987)