Intracellular Na+, K+ and Cl- activity in tonic and phasic muscle fibers of the crab Eriphia.
(1) Intracellular activities of K+, Na+ and Cl- were measured with ion-sensitive microelectrodes in four different types of muscle fibers in the closer muscle of the crab Eriphia. (2) The membrane resting potentials of the tonic fibers were 9-15 mV more positive than those of phasic muscle fibers. This was due to higher permeability of the membranes of tonic fibers for Na+. (3) The intracellular Na+-activity of tonic fibers was 35-40% higher than that of phasic fibers. Also intracellular Cl- -activity was about 15-33% higher in tonic fibers. (4) No significant differences in K+ -activities were found between physiologically different muscle fiber types. The K+ -equilibrium potentials were always more negative than the resting potentials. In muscle fibers with inhibitory innervation, Cl- -equilibrium potentials were close to (phasic fibers) or slightly more negative (tonic fibers) than resting potentials.
Hammelsbeck
M
M
Faculty of Biology, University of Konstanz, Federal Republic of Germany.
Rathmayer
W
W
D000818:Animals; D003386:Brachyura / Q000502:physiology*; D002712:Chlorides / Q000502:physiology*; D066298:In Vitro Techniques; D008564:Membrane Potentials; D009132:Muscles / Q000502:physiology*; D011188:Potassium / Q000502:physiology*; D012964:Sodium / Q000502:physiology*
D002712:Chlorides; D012964:Sodium; D011188:Potassium