Biomaterial Database

Ca2(+)-activated K+ channel from human erythrocyte membranes: single channel rectification and selectivity. 1991

P Christophersen

August Krogh Institute, Copenhagen, Denmark.

The Ca(+)-activated K+ channel of the human red cell membrane was characterized with respect to rectification and selectivity using the patch-clamp technique. In inside-out patches exposed to symmetric solutions of K+, Rb+, and NH+4, respectively, inward rectifying i-V curves were obtained. The zero current conductances were: K+ (23.5 pS +/- 3.2) greater than NH+4 (14.2 pS +/- 1.2) greater than Rb+ (11.4 pS +/- 1.8). With low extracellular K+ concentrations (substitution with Na+) the current fluctuations reversed close to the Nernst potential for the K ion and the rectification as well as the i-V slopes decreased. With mixed intracellular solutions of K+ and Na+ enhanced rectification were observed due to a Na+ block of outward currents. From bi-ionic reversal potentials the following permeability sequence (PK/PX was calculated: K+ (1.0) greater than Rb+ (1.4 +/- 0.1) greater than NH+4 (8.5 +/- 1.3) greater than Li+ (greater than 50); Na+ (greater than 110); Cs+ (much greater than 5). Li+, Na+, and Cs+ were not found to carry any current, and only minimum values of the permeability ratios were estimated. Tl+ was permeant, but the permeability and conductance were difficult to quantify, since with this ion the single channel activity was extremely low and the channels seemed to inactivate. The inward rectification in symmetric solutions indicate an asymmetric open channel structure, and the different selectivity sequences based on conductances and permeabilities reflect inter-ionic interactions in the permeation process.

UI	MeSH Term	Description	Entries
D011188	Potassium	An element in the alkali group of metals with an atomic symbol K, atomic number 19, and atomic weight 39.10. It is the chief cation in the intracellular fluid of muscle and other cells. Potassium ion is a strong electrolyte that plays a significant role in the regulation of fluid volume and maintenance of the WATER-ELECTROLYTE BALANCE.
D002118	Calcium	A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes.	Coagulation Factor IV,Factor IV,Blood Coagulation Factor IV,Calcium-40,Calcium 40,Factor IV, Coagulation
D002463	Cell Membrane Permeability	A quality of cell membranes which permits the passage of solvents and solutes into and out of cells.	Permeability, Cell Membrane
D004553	Electric Conductivity	The ability of a substrate to allow the passage of ELECTRONS.	Electrical Conductivity,Conductivity, Electric,Conductivity, Electrical
D004910	Erythrocyte Membrane	The semi-permeable outer structure of a red blood cell. It is known as a red cell 'ghost' after HEMOLYSIS.	Erythrocyte Ghost,Red Cell Cytoskeleton,Red Cell Ghost,Erythrocyte Cytoskeleton,Cytoskeleton, Erythrocyte,Cytoskeleton, Red Cell,Erythrocyte Cytoskeletons,Erythrocyte Ghosts,Erythrocyte Membranes,Ghost, Erythrocyte,Ghost, Red Cell,Membrane, Erythrocyte,Red Cell Cytoskeletons,Red Cell Ghosts
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000641	Ammonia	A colorless alkaline gas. It is formed in the body during decomposition of organic materials during a large number of metabolically important reactions. Note that the aqueous form of ammonia is referred to as AMMONIUM HYDROXIDE.
D012413	Rubidium	An element that is an alkali metal. It has an atomic symbol Rb, atomic number 37, and atomic weight 85.47. It is used as a chemical reagent and in the manufacture of photoelectric cells.
D015221	Potassium Channels	Cell membrane glycoproteins that are selectively permeable to potassium ions. At least eight major groups of K channels exist and they are made up of dozens of different subunits.	Ion Channels, Potassium,Ion Channel, Potassium,Potassium Channel,Potassium Ion Channels,Channel, Potassium,Channel, Potassium Ion,Channels, Potassium,Channels, Potassium Ion,Potassium Ion Channel