Denervation-activated inward rectifier in frog slow skeletal muscle fibers.
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.
Huerta
Miguel
M
Unidad de Investigación Enrico Stefani del Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, Apartado Postal 11, México. huertam@cgic.ucol.mx
Vásquez
Clemente
C
Trujillo
Xóchitl
X
Muñiz
Jesús
J
Trujillo-Hernández
Benjamin
B
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
D024661:Potassium Channels, Inwardly Rectifying; D001464:Barium