Comparison of the generation of platelet-activating factor and leukotriene C₄ in human eosinophils stimulated by unopsonized zymosan and by the calcium ionophore A23187: The effects of nedocromil sodium

The generation of platelet-activating factor (PAF) and leukotriene C₄ (LTC₄) from normodense human eosinophils (EOSs), stimulated with unopsonized zymosan or calcium ionophore A23187, has been studied. There was a zymosan time- and dose-dependent increase in both PAF and LTC₄ production. A plateau of 0.11 ± 0.04 ng of PAF per 10⁶ EOSs (mean ± SEM; n = 7) and of 1.38 ± 0.58 ng of LTC₄ per 10⁶ EOSs (n = 5) was reached at 5 × 10⁸ zymosan particles at 37 ° C for 30 minutes. Under optimal conditions, 91 ± 1% of the PAF and 66 ± 13% of the LTC₄ remained cell associated. Calcium ionophore A23187 induced a time- and dose-dependent increase in the quantities of PAF and of LTC₄ generated by EOSs. A plateau of 31 ± 13 ng of LTC₄ per 10⁶ EOSs (n = 5) was reached at 1 μmol/L of calcium ionophore A23187 at 37 °C for 15 minutes. The dose response for PAF generation reached 4.2 ± 0.8 ngl10⁶ EOSs (n = 8) at 10 μmol/L of calcium ionophore A23187 at 37 °C for 15 minutes and had not plateaued; 90 ± 5% of the generated PAF was cell associated. In vitro preincubation of EOSs with 10^-8 to 10^-4 mol/L of nedocromil sodium for 15 minutes did not change the subsequent generation or cellular distribution of PAF or LTC₄ in EOSs optimally stimulated with either zymosan or calcium ionophore A23187.