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Ionic currents in the node of Ranvier bathed in Na-free acid solutions (pH 3.4-4.6) were measured under voltage clamp conditions. Small (less than 0.1 nA) inward currents were detected in Na-free solutions at pH less than 4.0, whereas only outward currents were observed in Na-free solutions at normal pH. These currents have kinetics and voltage dependence(More)
The inhibition of the sodium current in nodal membrane at low pH external solutions was studied under voltage clamp conditions. Analysis of the data for membrane potentials from +10 to +150 mV shows that the inhibition of the Na+ currents at high positive potentials cannot be described by a titration curve of a single acid group. The data can be explained(More)
Ca2(+)-permeable channels in human carcinoma A431 cells were studied using the patch clamp technique. We have found two types of Ca2(+)-permeable channels which are activated by inositol 1,4,5-trisphosphate (IP3) applied to the intracellular side of the plasma membrane. Unitary conductances of these channels are 3.7 and 13 pS (105 mM Ca2+ in recording(More)
Ionic currents through sodium channels in nodal membranes were measured under voltage clamp conditions both at normal and at low (4.8-4.9) external solution pH. The measurements of so-called 'instantaneous' currents were used to distinguish between the proton blockage in open channels and the influence of low pH on channel gating processes. It is shown that(More)
Currents through normal and batrachotoxin-modified sodium channels in frog nerve were measured under voltage clamp conditions. Measured reversal potentials and the Goldman equation were used to calculate relative permeabilities. The permeability ratios were: PNa: PNH4: PK = 1: 0.47: 0.19. Hydrogen-to-sodium permeability ratio was estimated from reversal(More)
The activity of potassium channels of canine aortic sarcoplasmic reticulum was measured using the planar lipid bilayer-fusion technique. The channels have a conductance of 208 pS (400/100 mM K+ in cis/trans solutions) and potassium-to-sodium permeability ratio of 7.7 Ba2+ ions produced two main effects: one is the interruption of channel currents for tens(More)
Aluminium fluoride (AlF4-), a G protein activator, was used to study a possible role of G protein in the control of the pathways for Ca2+ influx through plasma membrane of human carcinoma A431 cells. Fluorimetric measurements with the Ca2+ indicator Indo-1 have shown that addition of fluoride induces an increase in concentration of cytosolic free calcium(More)
1. The steady-state characteristics of the sodium channel gating in the nodal membrane were determined under voltage clamp conditions before and after treatment with toxins from the venom of scorpion, Buthus eupeus. 2. The apparent binding constant (KA) of the toxin was determined for different levels of the membrane potential. At potentials more negative(More)
1. To study mechanisms of receptor-operated Ca2+ influx in non-excitable cells, membrane currents of rat peritoneal macrophages were recorded using whole-cell cell-attached and outside-out configurations of the patch clamp technique. Under whole-cell recording conditions, ATP applied in micromolar concentrations elicited an inward current response when the(More)