Potassium movement in patients with familial periodic paralysis: Relationship to the defect in muscle function

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Study in two patients with familial periodic paralysis and in one with non-familial periodic paralysis of potassium movement and associated changes in muscle function yielded the following results: 1. 1. The administration of glucose produced a greater fall in venous potassium concentration in these patients than in normal subjects, probably owing to greater uptake of the ion by muscle. 2. 2. The administration of epinephrine may have produced greater uptake of potassium by muscle in these patients than in normal subjects, but the difference was less marked than in the case of glucose. 3. 3. The administration of insulin resulted in evidence of movement of potassium into muscle, in contrast to movement out of muscle in normal subjects. 4. 4. Attacks of weakness which occurred spontaneously or following the administration of food, glucose or insulin were associated with reduced plasma potassium concentration and abnormally high arteriovenous difference, indicating abnormal uptake of the ion by muscle, and with reduction in muscle responsiveness to nerve stimulation and acetylcholine, in propagation of excitation, and in contractility. 5. 5. In these patients muscle contraction during attacks, even though very weak, caused more loss of potassium from muscle and greater increase in muscle responsiveness and contractility than prior to the attack, or than in normal subjects. 6. 6. Spontaneous recovery from weakness was associated with leakage of potassium from muscle, and was accelerated by exercise. During recovery following the administration of potassium chloride there was, first, slight improvement in strength which was followed by loss of potassium from muscle, and then more rapid improvement. 7. 7. The weakness of periodic paralysis appears to be due to the following sequence: (1) abnormal uptake of potassium by muscle; (2) marked increase in the intracellular to extracellular concentration ratio of this ion; (3) hyperpolarization of the muscle membrane; and (4) reduction in muscle responsiveness to nerve stimulation, in propagation of excitation, and in contractility.