ADULT RESPIRATORY-DISTRESS SYNDROME - ROLES OF LEUKOTRIENE C-4 AND PLATELET ACTIVATING FACTOR

The relationship between leukotriene C4 (LTC4), platelet activating factor (PAF), and adult respiratory distress syndrome (ARDS) was studied in nine patients and 84 control subjects. A leukocyte adherence inhibition (LAI) assay induced by each of the ligands was used to monitor the subjects for 3 consecutive days or until clinical recovery was noted. LAI was considered to be positive if the nonadherence index (NAI) was > 30 for LTC4 or > 20 for PAF. LAI was negative in all healthy subjects using both ligands. LTC4-induced LAI was positive in all nine ARDS patients and reverted to negative after recovery from the syndrome, while three (33.3%) of nine patients responded to PAF. In contrast, of the 84 control subjects, LAI was induced by LTC4 in only three (3.3%) and by PAF in five (5.9%). The mean NAI (52.2 ± 18) of LTC4-induced LAI in ARDS patients was significantly (p < .05) higher when compared with the control group (-5 ± 6.4), whereas that of PAF-induced LAI was < 20 in both groups, indicating that LTC4 is a more specific ligand than PAF. All three patients in whom ARDS was caused by sepsis responded to both LTC4 and PAF, but results of specific receptor-antagonist experiments indicated that each compound acted independently. The mean NAI for LTC4 (58.5 ± 10) and PAF (49.1 ± 12) in patients with septic ARDS were significantly (p < .05) higher when compared with those of patients with sepsis alone (0.5 ± 9.9 and 4.4 ± 17, respectively). The results of this study support the view that LTC4 and PAF may be involved in the pathogenesis of ARDS, and suggest that the LAI assay may be useful for early diagnosis and monitoring of disease status.