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Two cases of adynamia episodica hereditaria: In vitro investigation of muscle cell membrane and contraction parameters
Author(s) -
LehmannHorn Frank,
Rüdel Reinhardt,
Ricker Kenneth,
Lorković Hrvoje,
Dengler Reinhard,
Hopf Hanns Christian
Publication year - 1983
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.880060206
Subject(s) - depolarization , contraction (grammar) , membrane potential , chemistry , potassium , biophysics , tetrodotoxin , sodium , excitatory postsynaptic potential , muscle contraction , medicine , endocrinology , biochemistry , biology , receptor , organic chemistry
Membrane potentials, current–voltage relationships, and contractile parameters were studied in intact muscle cell bundles obtained from two patients with adynamia episodica hereditaria. In a normal extracellular medium, the cell membranes had resting potentials of about –80 mV and their current–voltage relationships were not significantly different from control curves. In contrast to normal muscles the afflicted cells were paralyzed in a medium having 6–10 mmol/liter potassium. The mechanisms of paralysis in the two specimens were different from each other. Many fibers from one patient were spontaneously active even in normal solution. In high potassium solution spontaneous activity was increased and the cells gradually depolarized to values at which excitatory sodium current is normally inactivated. This depolarization was connected with an increased sodium conductance and was reversed by the application of tetrodotoxin (TTX). The fibers from the other patient were not spontaneously active. In high potassium solution they were paralyzed at membrane potential values at which normal fibers would still contract. The reason for this paralysis was a reduced excitability.