title: Differential effects of halothane on adult and juvenile sodium channels in human muscle.
abstract: Myoballs were cultured from biopsies of adult human skeletal muscle. Transient currents through the sodium channels were elicited by depolarizing a myoball membrane with the whole-cell patch-clamp technique. The properties of the sodium channels were determined from the Hodgkin-Huxley parameters (INa max, tau m, tau h, h infinity-curve) derived from these transients. Halothane, when applied at 3.4 mmol/l (approximately 15 kPa), blocked about 50% of the current through the adult, TTX-sensitive sodium channels but had little effect on the current through the juvenile, TTX-insensitive sodium channels. At greater than 12 mmol/l, halothane blocked both channel types completely. The time constants of activation and inactivation were decreased in the presence of 3.4 mmol/l halothane but not enough to account for the decrease of the current amplitude. Halothane shifted the h infinity-curves of both channel types toward more negative potentials by an amount that was roughly proportional to its concentration. Myoballs from a man susceptible to malignant hyperthermia (MH) gave the same results as the controls indicating that the halothane effect on the action potential of MH-susceptible muscle are not mediated by a specific effect on the sodium channels.
authors.affiliation: Abteilung für Allgemeine Physiologie, Universität Ulm, Federal Republic of Germany.
authors.forename: J P
authors.initials: JP
authors.lastname: Ruppersberg
authors.forename: R
authors.initials: R
authors.lastname: Rüdel
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D002118:Calcium / Q000378:metabolism; D006221:Halothane / Q000494:pharmacology*; D006801:Humans; D008305:Malignant Hyperthermia / Q000503:physiopathology; D009132:Muscles / Q000187:drug effects* / Q000648:ultrastructure; D015222:Sodium Channels / Q000187:drug effects* / Q000502:physiology / Q000503:physiopathology; D013997:Time Factors
chemical_list: D015222:Sodium Channels; D002118:Calcium; D006221:Halothane