ATPase activity of kidney mitochondria stimulated by sodium

ATPase activity of intact mitochondria may be induced by the presence of sodium. Mitochondria obtained from kidney cortex or medulla demonstrate a higher sodium-stimulated ATPase than mitochondria prepared from liver. This difference is not due to a greater capacity of kidney mitochondria for ATP hydrolysis. Sodium-stimulated ATPase activity of mitochondria is not further enhanced by magnesium or potassium, nor is it inhibited by ouabain. Furthermore, the ATPase of submitochondrial particles is not enhanced by the presence of sodium. These results indicate that the ATPase activity of mitochondria which is stimulated by sodium is unrelated to the microsomal Na-K-ATPase. mitochondrial sodium-stimulated ATPase is affected by pH, anionic composition, furosemide, and ethacrynic acid. The demonstration that mitochondrial ATP hydrolysis can be activated by sodium suggests that intracellular sodium may directly influence intracellular energy metabolism.