title: Denervation-activated inward rectifier in frog slow skeletal muscle fibers.
abstract: We tested whether the absence of an inward rectifier channel in slow skeletal muscle fibers of the frog is regulated by innervation. Normal and denervated slow fibers were identified according to their passive electrical properties. In current-clamp experiments, anomalous rectification was quantified as the ratio of effective resistances for hyperpolarizing and depolarizing pulses. In isotonic potassium solution, this ratio was 0.45 +/- 0.1 (n = 14) for twitch fibers, whereas slow fibers displayed linear behavior [ratio = 1.0 +/- 0.05 (n = 15)]. However, denervated slow fibers showed anomalous rectification (ratio, 0.48 +/- 0.07; n = 5). This finding was supported by voltage-clamp experiments in which denervated slow fibers displayed (1) an inward rectifier current during hyperpolarizing pulses, (2) an increase in this current when [K(+)](o) was increased, and (3) a current inhibition after application of Ba(2+). These results suggest that frog slow fibers, which normally do not possess inward rectifier channels, can express them after denervation.
authors.affiliation: Unidad de Investigación Enrico Stefani del Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, Apartado Postal 11, México. huertam@cgic.ucol.mx
authors.forename: Miguel
authors.initials: M
authors.lastname: Huerta
authors.forename: Clemente
authors.initials: C
authors.lastname: Vásquez
authors.forename: Xóchitl
authors.initials: X
authors.lastname: Trujillo
authors.forename: Jesús
authors.initials: J
authors.lastname: Muñiz
authors.forename: Benjamin
authors.initials: B
authors.lastname: Trujillo-Hernández
mesh_terms: D000818:Animals; D001464:Barium / Q000494:pharmacology; D003714:Denervation; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000145:classification / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D024661:Potassium Channels, Inwardly Rectifying / Q000378:metabolism*; D011894:Rana pipiens
chemical_list: D024661:Potassium Channels, Inwardly Rectifying; D001464:Barium