Measurement of Intracellular pH

Intracellular pH regulation is critical for most cellular processes, including cell volume regulation, vesicle trafficking, cellular metabolism, cell membrane polarity, muscular contraction, and cytoskeletal interactions (1 –6 ). Changes of intracellular pH (pH_i ) affect the concentration of intracellular messengers like Ca²⁺ and cAMP and thus influence cellular signaling (7 ,8 ). In addition, some growth-stimulating signals, including epidermal growth factor, platelet-derived growth factor, insulin, vasopressin, and serum, activate sodium—proton exchange activity to induce cellular alkalinization, which is important in cell activation, growth, and proliferation (9 –13 ).