PRIMING EFFECT OF PLATELET-ACTIVATING-FACTOR ON LEUKOTRIENE C4 FROM STIMULATED EOSINOPHILS OF ASTHMATIC-PATIENTS

Background - Eosinophils from asthmatic patients are known to release greater amounts of leukotrienes than normal eosinophils when stimulate d by the calcium ionophore A23187. The effect of platelet activating f actor (PAF) in priming eosinophils was investigated. Methods - Eosinop hils were obtained from 18 asthmatic patients and 18 healthy donors. C ells separated by the Percoll gradients were incubated with PAF(C-18) for 30 minutes and then stimulated with the calcium ionophore A23187 ( 2.5 mu M) for 15 minutes. The amount of leukotriene C4 (LTC4) in super natants was measured using a combination of high pressure liquid chrom atography and radioimmunoassay. Results - The mean (SD) amount of LTC4 released by eosinophils from asthmatic patients upon stimulation with the calcium ionophore A23187 alone was 27.9 (9.9) ng/10(6) cells (n=6 ). The amount of LTC4 released following stimulation with the calcium ionophore A23187 after pretreatment with PAF (1, 5, and 10 mu M) was 5 7.2 (8.9), 75.1 (14.3), and 52.6 (10.7) ng/10(6) cells (n=6), respecti vely. Trace amounts of LTC4 (0.9 (0.02) ng/10(6) cells, n=6) were dete cted in the supernatant of the cells after stimulation by PAF alone (5 mu M). The amount of LTC4 released upon stimulation by calcium ionoph ore A23187 alone in eosinophils from healthy donors was 10.3 (3.7) ng/ 10(6) cells (n=4). The amounts of LTC4 released upon stimulation with calcium ionophore A23187 after pretreatment with PAF at concentrations of 1, 5, and 10 mu M were 11.9 (3.5), 17.8 (5.6), and 12.7 (5.1) ng/1 0(6) cells (n=4), respectively. Trace amounts of LTC4 (0.6 (0.02) ng/1 0(6) cells, n=4) were detected in the supernatant of the cells upon st imulation with PAF alone (5 mu M). The amounts of LTC4 released upon s timulation with calcium ionophore A23187 after pretreatment with lyso- PAF at concentrations of 1, 5, and 10 mu M (n=4 or 6) were 30.8 (5.2), 22.9 (5.1), and 27.3 (4.3) ng/10(6) cells (n=6) from the eosinophils of asthmatic patients and 13.7 (3.3), 15.2 (4.9), and 14.7 (3.8) ng/10 (6) cells (n=4) from the eosinophils of healthy donors. Conclusions - The results indicated that PAF enhanced LTC4 formation by eosinophils obtained from asthmatic patients stimulated with the calcium ionophore A23187, but not those obtained from normal subjects.