Heterogeneity of basal intracellular calcium concentration and its relations to the reactivity in mouse peritoneal macrophages

AIM: To investigate the heterogeneity of basal intracellular free calcium concentration(Ca²⁺]_i) in peritoneal macrophages(PM) and whether it is relative to the reactivity of PM at the single cell level. METHODS:Ca²⁺]_iimplicated stimulated were measured by fluorescent microscopic imaging system after loading with fluorescent probe fura-2/AM. Superoxide(O₂^-)produced by single PM was determined by modified NBT test. RESULTS: The values of basalCa²⁺]_idetermined in 392 PMs of 7 mice showed normal distribution (54±24) nmol/L, n=392] with wide range(less than 20 nmol/L to more than 100 nmol/L), among which about 50% were in the range of 40-60 nmol/L. When stimulated with PMA or fMLP,Ca²⁺]_iwas increased, the peak values were positively correlated with the basalCa²⁺]_iin one mouse(PMA stimulated cells: r=0.52, P<0.01, n=58; fMLP stimulated cells:r=0.59, P<0.01, n=44. Both of the experiments were repeated in 3 mice, the results in the other 2 mice were similar). The O₂^- in PMA stimulated PMs were also positively correlated with the basal i(r=0.42, P<0.01, n=43, repeated in 4 mice, the results in the other 3 mice were similar). CONCLUSION: BasalCa²⁺]_iin murine PM is heterogeneous, and the value of basalCa²⁺]_iis tightly correlated to the reactivity of PM stimulated by proinflammatory factors.