Changes in cellular and subcellular composition during potassium deficiency.

1. A specific dietary deficiency of potassium in young rats reduced the potassium concentration in thigh muscle by 48%, and in heart and kidney by 18%, but did not significantly affect the concentration in liver or brain. Conversely the sodium concentration rose in liver, heart and thigh muscle, and thigh muscle also accumulated increased amounts of magnesium. Apart from an increase in the water content of many tissues, no consistent changes in the composition of major cell constituents were observed. 2. The loss of potassium and accumulation of sodium and magnesium occurred predominantly in the supernatant fraction of the cell. The supernatant of all tissues studied contained about 80% of the total cellular potassium and sodium, and the potassium was present entirely in the ionic form. 3. Potassium and magnesium are the two most abundant intracellular metals, but their deficiencies have very different effects on the cell. The relationship between them is more complex than the inverse relationship between potassium and sodium.