Fig. 5
From: Muscle sodium content in patients with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome
Illustration of the lower leg cross-section with exemplary representation of intracellular and extracellular sodium in the muscle tissue. The zoomed section on the right shows a myocyte with all its channels and transporters involved in the handling of protons, sodium, calcium, and potassium. Physiologically, the NCX works in forward mode to export calcium. High sodium concentration caused by high NHE1- and low Na+/K+-ATPase activity can reverse the transport direction of the NCX to import calcium instead of exporting it, resulting in calcium overload