Selectivity and sensitivity to hydrogen ion blocking of batrachotoxin-modified sodium channels in nerve fiber membrane |
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Authors: | G N Mozhaeva A P Naumov B I Khodorov |
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Abstract: | Currents through batrachotoxin-modified sodium channels were measured by the voltage clamp method on the Ranvier node membrane. In experiments with replacement of Na+ in the external solution by K+ or NH 4 + the following series of permeabilities, determined as reversal potentials according to the equation of a static field, was obtained — PNa: \(P_{NH_4 }\) :PK=1:0.47:0.19. The relative permeability for H+ was determined by measuring currents after replacement of Na+ in the external solution by nonpenetrating choline ions and lowering pH to 3.7–3.8. The ratio pH/pNa for sodium channels modified by batrachotoxin averaged 528±46. Modified channels were less sensitive to the blocking action of H+ than normal sodium channels. The difference in the effective values of pK of the acid group of normal and modified channels was 0.40–0.45. |
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