BLT1 is the major receptor mediating LTB4-induced calcium mobilization in human monocytes. (A) The relative mRNA expression of CysLT1, CysLT2, GPR17, BLT1 and BLT2 measured by TaqMan is expressed per thousand copies of the control GAPDH gene and presented as mean values ± SD of 3 healthy donors. Monocytes were stimulated with LTB4 (50 nmol/L) in the presence of increasing concentrations of CP105696 (B), or LTB4, 12-HETE, 12-HHT (500 nmol/L) (C) or LTB4 in presence of LY255283 (200 nmol/L) (D) or vehicle control (10 min pretreatment). (E) Monocytes were nucleofected with BLT1 or BLT2 siRNA or negative control oligonucleotides (NC siRNA) as described in the Methods section, cultured for 24 hours and calcium flux was measured in response to LTB4 (100 or 10 nmol/L). Results of calcium flux experiments are shown as relative light units (RLU) from the FLEX 3 station. For the calcium flux experiments, the data are from one of three separate experiments each with similar results.