Ca2+-activated K+ conductance of human red cell membranes exhibits two different types of voltage dependence |
| |
Authors: | Per Stampe Bent Vestergaard-Bogind |
| |
Institution: | (1) Zoophysiological Laboratory B, August Krogh Institute, University of Copenhagen, DK-2100 Copenhagen Ø, Denmark |
| |
Abstract: | Summary The voltage dependence for outward-going current of the Ca-activated K+ conductance (g
k (Ca)) of the human red cell membrane has been examined over a wide range of membrane potentials (V
m) at constant values of K+]ex, K+]c and pHc, the intact cells being preloaded to different concentrations of ionized calcium. Outward-current conductances were calculated from initial net effluxes of K+ and the corresponding (V
m-Ek) values. The basic conductance, defined as the outward-current coductance at (V
m-Ek) 20 mV and K+]ex 3mM (B. Vestergaard-Bogind, P. Stampe and P. Christophersen,J. Membrane Biol.
95:121–130, 1987) was found to be a function of cellular ionized Ca. At all degrees of Ca activationg
K(Ca) was an apparently linear function of voltage (V
m range –40 to +70 mV), the absolute level as well as the slope decreasing with decreasing activation. In a simple two-state model the constant voltage dependence can, at the different degrees of Ca activation, be accounted for by a Boltzmann-type equilibrium function with an equivalent valence of 0.4, assuming chemical equilibrium atV
m=0 mV. Alternatively, the phenomenon might be explained by a voltage-dependent block of the outward current by an intracellular ion. Superimposed upon the basic conductance is the apparently independent inward-rectifying steep voltage function with an equivalent valence of 5 and chemical equilibrium at the givenE
K value.Abbreviations CCCP
carbonyl cyanidem-chlorophenylhydrazone
- DIDS
4,4 -diisothiocyanostilbene-2,2 -disul |
| |
Keywords: | Ca2+-activated K+ conductance human red cell membrane function of cellular calcium voltage dependence |
本文献已被 SpringerLink 等数据库收录! |
|