Fig. 1

Schematic representation of K⁺, Na⁺ and Tl⁺ transport across cellular membranes. Sodium–potassium pump (Na⁺/K⁺-ATPase) transports K⁺ ions inside and Na⁺ ions outside a cell against their concentration gradient using energy released by the hydrolysis of ATP. Tl⁺ ions, which mimic K⁺ physiological behaviour, can be transported inside the cell via potassium channels, such as the sodium–potassium pump. Tl⁺ transport mechanism outside the cell is currently unknown