We studied the metabolism of 3H-platelet activating factor (PAF) and lyso-PAF in human polymorphonuclear granulocytes (PMN) from severely burned patients (n = 6) on days 1, 5, 9, 15, and 25 post-trauma. All patients suffered from a severe burn trauma of more than 30% total body surface area. Stimulation of PMN in healthy donors (n = 10) with the Ca-ionophore resulted in the conversion of 3H-lyso-PAF into PAF (18 +/- 2% of total radioactivity) and alkyl-acyl-glycero-phosphorylcholine (alkyl-acyl-GPC, 50 +/- 6%). In burned patients a significantly reduced formation of 3H-PAF was observed between days 1 and 15 post-trauma (day 9: 1 +/- 1%, p less than 0.0001). This pattern was normalized again in patients (n = 5) who survived the trauma after septic periods and was observed during the second week post-trauma. In one patient who succumbed to his injuries a sustained inhibition of PAF formation was observed up to his death. The decreased formation of PAF correlated weakly with the appearance of immature granulocytes within the analyzed cell fraction (ratio of immature cells versus PAF-formation, r = -0.55, p = 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)