Cadmium as a tool for studying calcium-dependent cation permeability of the human red blood cell membrane.
Three Ca(2+)-dependent procedures known to increase cation permeability of red blood cell membranes were tested with Cd2+ ions which equal Ca2+ ions both in their charge and the crystal radius, 1. Increase of non-selective permeability for monovalent cations by incubating the red cells in a Ca(2+)-free sucrose medium. Addition of Cd2+ to the suspension of leaky cells failed to restore the initial impermeability of the red cell membrane while a repairing effect of Ca2+ was evident both in the presence and absence of Cd2+. Thus, in low electrolyte medium, Cd2+ could neither mimic Ca2+, nor prevent the latter from interacting with membrane structures which control cation permeability. 2. Increase of the K(+)-selective permeability by propranolol plus Ca2+. Cd2+ added to a Ca(2+)-free Ringer type medium containing propranolol enhanced K+ permeability similar to that obtained with Ca2+. No changes of membrane permeability could be detected in the presence of 0.5 mmol/l Cd2+ in absence of propranolol. The Cd(2+)-stimulated K+ channels were different from those induced by Ca2+. They proved to be insensitive to quinine, exhibited a low K+/Na+ selectivity, and showed no tendency to self-inactivation. 3. Stimulation of K+ permeability by electron donors plus Ca2+. Substitution of Ca2+ by Cd2+ yielded results similar to those obtained with propranolol. The ability of Cd2+ to overtake the role of Ca2+ appears to depend on the system studied. It supplies information allowing to distinguish between the diverse Ca(2+)-dependent systems in cell membranes.
Skulskii
I A
IA
Institute of Evolutionary Physiology and Biochemistry, Acad. Sci. USSR, Sankt-Peterburg.
Glasunov
V V
VV
Manninen
V
V
D001205:Ascorbic Acid / Q000494:pharmacology; D002104:Cadmium / Q000494:pharmacology*; D002118:Calcium / Q000494:pharmacology*; D002412:Cations / Q000378:metabolism*; D002463:Cell Membrane Permeability / Q000187:drug effects*; D004910:Erythrocyte Membrane / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D007473:Ion Channels / Q000378:metabolism; D008560:Membrane Fluidity / Q000502:physiology; D008773:Methylphenazonium Methosulfate / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D011433:Propranolol / Q000494:pharmacology; D013395:Sucrose / Q000494:pharmacology
D002412:Cations; D007473:Ion Channels; D002104:Cadmium; D008773:Methylphenazonium Methosulfate; D013395:Sucrose; D011433:Propranolol; D001205:Ascorbic Acid; D011188:Potassium; D002118:Calcium