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Human red blood cells studied by means of whole-cell and nystatin-perforated patch-clamp
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Voltage-dependent outward currents in human RBC recorded with patch-clamp whole-cell (A) and nystatin-perforated patch (B) techniques. Positive step potentials imposed starting from a holding potential of 0 mV up to 84 mV induced a slow-activating non-inactivating outward current. The current activation in (A) and (B) fitted well to the double exponential equation.
Red blood cells (RBC) are subjected to widely differing conditions in the circulation. For instance, they pass in a few seconds from 300 up to 1400 mosM during their transit through the vasa recta in the kidney. They must also adapt to rapid changes in volume and shape when they flow from arterioles to capillaries. These changes require great adaptability.
There are very few studies on human RBC using the whole-cell patch-clamp and perforated-patch technique. This is mainly because of the technical difficulties inherent to patch-clamping these cells. These methods allow recordings utilizing salt solutions at physiological concentrations. Furthermore, the channels formed by the nystatin in the perforated-patch, which are permeable to monovalent ions but exclude multivalent ions and molecules as large as or larger than glucose, avoid the dialysis of important substances from the erythrocyte’s cytoplasm.
Changes in ionic gradients across their membrane and stretch activation of cation channels might alter the membrane potential sensed by the voltage-dependent cation channels. In turn, these channels can open with a time constant consistent with the rapid changes required by the circulation.
The permeability to cations of the human RBC membrane increases when changes in the extracellular medium induce a more positive membrane potential. This current may be involved in the rapid adaptations of these cells in the circulation, cell volume regulation and blood clot formation.
See also: The red cell review
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