Modification of C1- transport in skeletal muscle of Rana temporaria with the arginine-binding reagent phenylglyoxal.
1. The effect of membrane modification by the arginine-binding reagent phenylglyoxal (PG) on Cl- permeability was studied in thin bundles of twitch fibres from frog muscle. The bundles were modified by a method that yields stable PG binding to outer arginyl residues in erythrocyte membranes. 2. PG almost eliminated the pH-dependent fraction of 36Cl- efflux under conditions of Cl- equilibrium in depolarized bundles: the fluxes at pH 7.2 and 8.5 were strongly inhibited approaching an apparent baseline value close to the normal flux at pH 6 which per se was not inhibited. 3. The uninhibited flux at pH 6 in modified bundles maintained the normally high sensitivity to 4,4'-dinitro-stilbene-2,2'-disulphonate (DNDS), and the reduction of fluxes at pH > 7 coincided with increased DNDS sensitivity, suggesting a selective blocking of the pH-dependent flux fraction that has a low DNDS sensitivity. 4. In normal Ringer solution the modified fibres showed normal resting membrane potentials (Vm) with normal sensitivity to [K+]o but sensitivity to changes of [Cl-]o was almost eliminated, suggesting a normal resting Na+:K+ conductance ratio (gNa/gK) and that the main influence of modification on the resting membrane conductance (gm) was a loss of Cl- conductance (gCl). 5. The modified fibres were not excitable, possibly due to arginine modification in the voltage sensor (S4) of the Na+ channels. 6. These results suggest that positively charged arginines are important for the activity of the pH-dependent Vm-stabilizing Cl- channels and that PG may isolate a pH-independent basal flux fraction which normally dominates the Cl- flux at low pH.
Skydsgaard
J M
JM
Department of Medical Physiology, Panum Institute, University of Copenhagen, Denmark.
D000818:Animals; D001120:Arginine / Q000502:physiology*; D018118:Chloride Channels / Q000187:drug effects / Q000378:metabolism*; D004558:Electric Stimulation; D004594:Electrophysiology; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004910:Erythrocyte Membrane / Q000187:drug effects / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000378:metabolism; D018482:Muscle, Skeletal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D010658:Phenylglyoxal / Q000494:pharmacology*; D011896:Rana temporaria; D013267:Stilbenes / Q000494:pharmacology
D018118:Chloride Channels; D004791:Enzyme Inhibitors; D013267:Stilbenes; C022306:4,4'-dinitro-2,2'-stilbenedisulfonic acid; D001120:Arginine; D010658:Phenylglyoxal