Potassium and Its Disorders

Abstract

Potassium is the major intracellular cation in the human body. Over 98% of the total body potassium is located within the intracellular compartment. In healthy adults, the total intracellular content of potassium is equivalent to 3000-3500 mmol. Approximately 70% of this amount is found in skeletal muscle with lesser amounts in bone, red blood cells, liver and skin. The extracellular compartment contains 1-2% of the total body potassium. This uneven distribution of total body potassium is the result of an electro-genic pump, Na + , K + ATPase. This pump transports three sodium ions extracellularly in exchange of transporting two potassium ions intracellularly. This mechanism creates a ratio that determines the cell membrane potential. Maintenance of this potassium ratio and membrane potential is vital for normal nerve conduction and muscular contraction. 1. Potassium physiology and homeostasis The kidney is responsible for maintaining the total body potassium content by matching intake with excretion. Insulin and catecholamines are primarily responsible for the regulation and distribution of potassium between the intracellular and extracellular compartments [21]. Other factors that can alter the distribution of potassium between compartments include acid-base disorders, plasma osmolarity and exercise. The following section describes the effects of these factors in causing transcellular shifts of potassium.