In order for our cells to work properly, systems had to develop that could regulate the concentration of salt and other components of our blood and extracellular fluid.
In normal circumstances, more than ninety percent of the total body potassium is intracellular, the remaining is in the extracellular fluid and blood plasma.
Considering cells can't survive outside a narrow range of electrolyte levels in the extracellular fluid, the ability to retain salt and at the same time excrete excess salt is very important.
This is achieved by two mechanisms: excretion of potassium through the kidneys and intestines with the kidneys playing a predominant role, shifting of potassium from the extracellular fluid into the cells by the sodium potassium pump.