Membrane currents in human intercostal muscle at varied extracellular potassium.
Hyperpolarizing and depolarizing square steps were imposed on the membrane potential of excised human intercostal muscle fibers by means of a 3-microelectrode voltage clamp. The steady-state amplitudes of the membrane currents inducing such steps were investigated as a function of the membrane potential, while the muscle was bathed in solutions varying in potassium content (Ke = 1, 3.5, 7, 20, and 60 mM). At all potassium concentrations, the membrane acted as a rectifier, both in the inward- and outward-going directions. Inward currents were much reduced when Ke was lowered from 3.5 to 1 mM, and were increased when Ke was raised beyond 3.5 mM. The delayed outward current was reduced when Ke was increased from 3.5 mM to 7 mM and higher potassium concentration. The results were qualitatively similar to those reported for rat skeletal muscle.
D002462:Cell Membrane / Q000502:physiology; D002712:Chlorides / Q000494:pharmacology; D004553:Electric Conductivity; D006801:Humans; D007366:Intercostal Muscles / Q000187:drug effects / Q000502:physiology*; D007473:Ion Channels / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects; D011188:Potassium / Q000378:metabolism / Q000494:pharmacology*; D013779:Tetrodotoxin / Q000494:pharmacology
D002712:Chlorides; D007473:Ion Channels; D013779:Tetrodotoxin; D011188:Potassium