Effect of Mn²⁺ addition to Fura 2/AM-loaded T cells incubated with ASA. Mn²⁺ was used as substitute for Ca²⁺ and the more pronounced the quenching of the Fura 2/AM signal, the higher the Mn²⁺ influx. Cells were incubated in a Ca²⁺-free medium and stimulated (arrow) with ASA or no agent (medium). After incubation for 60 seconds, 25 μmol/L Mn²⁺ was added to the cell suspension. Fluorescence intensity was normalized to 100% just before Mn²⁺addition. Data are expressed as the mean SEM of 10 determinations. (*)P < .01