Leukotriene-induced mobilization of intracellular free calcium in CD34⁺ hematopoietic progenitors, mature leukocytes, and cell lines.

(A) Mobilization of intracellular calcium in isolated PB CD34⁺ cells was analyzed by flow cytometry using the green fluorescent calcium indicator Fluo-3. After addition of LTD4 (1 μM), time-dependent, relative (compared to baseline level = 1) changes of the mean fluorescence were recorded. Control, ●; LTD4, ▵. (B) LTD4-induced intracellular calcium mobilization (expressed as relative Fluo-3 fluorescence 5 seconds after addition of LTD4) in primary PB CD34⁺ progenitors was dose dependent, with an optimum concentration of 1 μM. (C) The LTD4-induced calcium release in PB CD34⁺ cells (expressed as relative Fluo-3 fluorescence 5 seconds after addition of LTD4) was completely blocked by the CysLT1 receptor antagonist MK-571 and partially reduced by PTX. Other cysteinyl leukotrienes (LTC4, LTE4 at 1 μM) were less effective. The noncysteinyl leukotriene LTB4 (1 μM) did not induce calcium fluxes in CD34⁺ cells. The response of BM-derived CD34⁺progenitors was similar to THP-1 cells, whereas the strongest calcium fluxes were observed in the KG1a cell line. LTD4 induced calcium mobilization also in mature PMNCs, which, however, was not suppressed by MK-571 and was less efficient than the noncysteinyl leukotriene LTB4.