The effects of terbium (III) on the Ca-activated, K channel found in the resealed human erythrocyte membrane.
Incorporated terbium, Tb3+, activates the Ca-activated K channel found in the resealed erythrocyte ghost membrane and allows the net efflux of K. As in the case of Ca activation, low levels of external K stimulate the net efflux of K. The action of incorporated Tb3+ seems to be analogous to that of incorporated Ca. Externally applied Tb3+, however, inhibits the net efflux of K after either Ca or Tb3+ activation. The net-efflux of K can be inhibited by Tb3+ even after partial digestion of the channel by low levels of incorporated trypsin. Furthermore, the channel when incorporated into planar bilayers, can be inhibited by Tb3+. Externally applied Tb3+ does not seem to inhibit net K efflux indirectly via inhibition of the pathways for the co-transported anions. In addition because of the low concentrations of Tb3+ required for inhibition, it seems unlikely that an alteration of surface potential is responsible for the observed effects.
Wood
P G
PG
Mueller
H
H
D002118:Calcium / Q000494:pharmacology*; D004910:Erythrocyte Membrane / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects*; D008051:Lipid Bilayers; D011188:Potassium / Q000378:metabolism*; D013194:Staining and Labeling; D013725:Terbium / Q000494:pharmacology*; D014357:Trypsin
D007473:Ion Channels; D008051:Lipid Bilayers; D013725:Terbium; D014357:Trypsin; D011188:Potassium; D002118:Calcium