A pH sensing mechanism capable of sensing lactic acidosis and regulating release of a cytokine on a time scale of minutes to hours during exercise may need to be distinct from the SNAT2 pH sensing mechanism because the latter operates on a longer time scale (hours to days) and functions in the sensing of chronic acidosis (for example in starvation ketoacidosis64) culminating in the release of free amino acids from muscle protein.18 Here, SLC38A2 is linked to lactic acidosis.