The potassium concentration in the blood is primarily regulated by the kidneys, where potassium channels (protein structures that pass potassium ions across cell membranes) in the cells of the distal tubules regulate potassium excretion in the urine.[1][2][3] Distribution of potassium within the body’s tissues is regulated by insulin, catecholamines (e.g., noradrenaline and adrenaline), and aldosterone.[2][3]
There is a steep gradient between the potassium concentration in the blood (i.e., the extracellular potassium concentration: 3.5 to 4.5 millimoles per liter, or mmol/L) and the potassium concentration in the cells (the intracellular concentration: 120 to 140 mmol/L). This gradient is critical for maintaining normal function in every cell in the body because it helps potassium ions constantly cross the cell membrane that separates the blood from the cell, generating a membrane potential. This vitally important membrane potential drives electrical impulses in neurons and contractions in muscle cells.[2][3]
This gradient is maintained by the potassium channels found in cell membranes. One of the most important is the sodium-potassium ATPase pump, which is found in every cell in the body and uses energy — adenosine triphosphate (ATP) — to maintain the potassium (and sodium) gradient across the cell membrane.[2][3]
The correlation between higher daily dietary potassium intake and a reduced risk of stroke and cardiovascular disease[4][5] [6][7] is likely explained by the blood-pressure-lowering effect of potassium.[8][9] While some evidence shows that potassium intake causes natriuresis — increased sodium excretion in the urine — and reduces vascular resistance,[3][8][10] it is not precisely understood how supplementation with potassium lowers blood pressure.