[Ionic conductivity of muscle fiber membranes of Locusta migratoria]

On muscle fibers from m. flexor tibiae of the locust studies have been made of the effect of rapid changes in potassium and chloride concentrations on the membrane potential (MP). The MP constituted 56.0 +/- 1.0 mV. The relationship between the MP and the external potassium at [K]o.[Cl]o equals const may be described by Nernst equation for two different intracellular concentrations of these ions, at [K]o less than or equal to 40 mM and at [K]o greater than or equal to 80 mM. From the relationship between the MP and rapid changes in [K]o or [Cl]o at constant concentration of correspondingly [Cl]o and K]o relative membrane conductivity for these ions were found (TK=0.55 and TC1=0.41). Using impulse analysis, electrical constants of muscle membrane were determined (lambda = 1.9 +/- 0.1 mm; Ri equals 103 +/- 7 ohm.cm; Rm = 1.430 +/- 76 ohm.cm2; Cm = 16 +/- 1 muF.cm-2). High values for Cm correlate with numerous invaginations in muscle membrane which were revealed in electron microscopis investigations. Active responses of the membrane are gradual. In the presence of ions of Sr they are transformed into regenerative action potentials.