Hypokalemic periodic paralysis: in vitro investigation of muscle fiber membrane parameters.

To study the mechanism of attacks in familial hypokalemic paralysis, we recorded resting membrane potentials, action potentials, current-voltage relationships, and isometric forces in intercostal muscle fibers from three patients. In normal extracellular medium, the resting potential was reduced, but membrane conductance was not different from control. Excitability was reduced and the action potentials had no overshoot.

The resting membrane parameters of human intercostal muscle at low, normal, and high extracellular potassium.

Membrane parameters at the respective resting potentials in low, normal, and high extracellular potassium solutions were determined in intercostal muscle fibers from 15 patients with no known neuromuscular disease. In synthetic interstitial fluid (normal potassium concentration 3.5 mmol/liter), we found the following mean values: resting membrane potential RP = -83.

Two cases of adynamia episodica hereditaria: in vitro investigation of muscle cell membrane and contraction parameters.

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.

Clinical study of paramyotonia congenita with and without myotonia in a warm environment.

Fourteen patients with paramyotonia congenita were examined clinically. Patients of 3 families had no myotonia in a warm environment while in a cold environment they developed paradoxical myotonia (myotonia aggravated by repeated muscle contraction). Patients of a 4th family had myotonia associated with after-activity in a warm environment which was not paradoxical.

Membrane defects in paramyotonia congenita with and without myotonia in a warm environment.

Three patients with paramyotonia congenita and 3 control persons were biopsied for an in vitro investigation of the sarcolemmal membrane parameters and of the contractile properties of paramyotonic muscle. At 37 degrees C, paramyotonic muscle fibers had normal resting potentials, but on cooling to 27 degrees C they depolarized. Depolarization to -60 mV caused spontaneous activity, and further depolarization to -40 mV caused inexcitability.