The effects of lyotropic anions on charge movement, calcium currents and calcium signals in frog skeletal muscle fibres.

Abstract

SUMMARY1. Intramembrane charge movement and Ca2+ currents were monitored in voltage-clamped segments of frog skeletal muscle fibres using the triple-Vaseline-gap technique. Calcium signals were measured in current-clamped fibres using either of the indicators Arsenazo III or Antipyrylazo III.2. Non-linear capacitative currents (charge 1) were obtained using a subtraction procedure which employed either a -20 mV control pulse from a holding potential of -100 mV or alternatively a control pulse to + 80 mV in depolarized fibres. The amount of charge mobilized depended on voltage according to a two-state Boltzmann function. The total charge (Qmax) was increased by ca 100% and the steepness parameter (k) by ca 70 % when a + 80 mV control pulse was used.3. Thiocyanate (SCN-) and other lyotropic anions reversibly shifted the voltage dependence of mobilized charge towards negative potentials. Qmax was not significantly affected. 'Off' charge tails were greatly prolonged by lyotropic anions.4. Extracellularly applied lyotropic anions affected the dihydropyridine-sensitive Ca2+ current by shifting the I-V relation toward more negative voltages and delaying deactivation of the tail currents.5. The effects of lyotropic anions did not depend on whether the anion was introduced intracellularly or extracellularly.6. Extracellular SCN-reversibly increased the peak amplitude and rate of rise of Ca signals, and decreased the latent period between stimulation and onset of the Ca signal.7. It is concluded that lyotropic anions have similar effects on Ca2+ currents and on charge movement.

Intracellular chloride modulates A‐type potassium currents in astrocytes

“…This idea appears to be consistent with the observation that A-type channels typically activate at more hyperpolarized potentials than their delayed rectifying counterparts. Taken together, the present studies demonstrate voltage-gated K ϩ channel activity to be highly electrostatic in nature and validate the possibility that anions alter electrostatic charges on or near the voltage sensor (Dani et al, 1983;MacKinnon et al, 1989;Delay et al, 1990;Green and Andersen, 1991;Thoreson and Stella, 2000).…”

“…Anion-mediated alterations in surface potentials have previously been shown to follow the lyotropic or Hofmeister anion series (Dani et al, 1983;Delay et al, 1990;Thoreson and Stella, 2000), where SO 4 2Ϫ and F Ϫ are equally less effective at altering surface potentials than Cl…”

Effect of sodium deprivation on contraction and charge movement in frog skeletal muscle fibres

“…The best fit parameters indicated in the legend are very similar to those reported from this laboratory in Na+-free solutions and high internal EGTA (Delay et al, 1990), indicating that charge movement is unaffected by heparin.…”

“…The triple-Vaseline-gap voltage-clamp technique as described elsewhere (Delay et al, 1990) was used. Fibres were dissected in normal Ringer's (solution A with Na +, Table 1) and laid in a chamber across three Glisseal seals (Borer Chemie, Switzerland), which divided the chamber into four pools.…”

The effects of lyotropic anions on electric field‐induced guidance of cultured frog nerves.

“…If decreasing membrane surface charge inhibits fieldinduced cathodal orientation, then treatments which increase the negative surface potential may enhance orientation. Lyotropic anions adsorb to lipid bilayers, making them more negatively charged (McLaughlin, Bruder, Chen & Moser, 1975) and shift the voltage dependence of ion channels to more negative levels (Dani, Sanchez & Hille, 1983;Delay, Garcia & Sanchez, 1990). We have examined the effect of the lyotropic anions SCN, Cl04-and s042-on electric field-induced neurite orientation.…”