THE RÔLE OF POTASSIUM IN PHYSIOLOGICAL PROCESSES

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Abstract
Potassium is an essential part of the physico-chemical structure of the cell. It is not fixed in position but can move about in the body rather freely according to the demands of shifting membrane equilibria. According to the best evidence at present this is a static equilibrium relatively uninfluenced by lack of oxygen. It probably moves in or out of cells when this equilibrium is disturbed by acid-base imbalances. It moves in when protoplasm grows and out when protoplasm disintegrates. It moves from cells to plasma under a variety of conditions all involving an excessive loss of NaCl and water from the body, i.e., hemorrhage, shock, adrenalectomy, intraperitoneal glucose soln., intestinal obstruction or fistulas. K moves into the blood during increased muscular activity or increased rate of metabolism and falls during rest or anesthesia. There is some evidence that it follows the carbohydrate cycle from muscle to liver and back again. It frequently rises and falls with the lactic acid level as in muscular exercise, hemorrhage, and asphyxia; likewise it frequently rises and falls with the sugar level, falling after insulin and rising (temporarily at least) after adrenalin. Possibly it moves from muscle to liver with lactic acid and from liver to muscle with sugar. To some extent, K is under the control of endocrines, being most specifically affected by the secretion of the adrenal cortex. In small concs. K is excitatory and in larger concs.it is inhibitory. In this capacity it is particularly effective and important in synapses or myo-neural junctions. It causes a contracture of skeletal muscle and an increase of tone in heart and smooth muscle under proper conditions. Its effects are usually inhibited by Ca. Since K and Ca modify the most fundamental properties of protoplasm and cells they play a secondary modifying role in nearly every vital process. Since the number of ways in which a physiological reaction can be modified are very limited (usually limited to "increase" or "decrease") it is quite possible to classify artificially many drugs, hormones, poisons or other influences as K-like or Ca-like or para-sympathetic and sympathetic with more apparent success than is really justified by the complexity of the situation.

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