The cation specificity of the potassium and gramicidin channels of muscle fiber membrane
Shvinka, N.E.; Caffier, G.
Tsitologiia 30(9): 1101-1107
1988
ISSN/ISBN: 0041-3771 PMID: 2464221 Document Number: 323220
Conductance ratios (Gi/Gk) and permeability ratios (Pi/Pk) for monovalent cations in frog muscle fibres have been defined under constant current conditions using a double sucrose gap method. Selectivity determined from potassium channel conductance is: K+ greater than Rb+ greater than Cs+ greater than greater than NH4+ greater than Na+ greater than Li+. In gramicidin channels both the permeability and conductance sequences are identical: NH4+ greater than Cs+ greater than Rb+ greater than K+ greater than Na+ greater than Li+. In isotonic K+-sulfate solution with one-sided addition of external [Tl+] (2.5 x 10(-3)-20 x 10(-3) M), differences in the conductance and permeability ratios for gramicidin channel were observed.