REPERFUSED GUT ELABORATES PAF THAT CHEMOATTRACTS AND PRIMES NEUTROPHILS

Our in vivo model of mesenteric ischemia/reperfusion (I/R) has shown t hat the gut serves as a priming bed for neutrophils (PMN). Activation of phospholipase A(2) (PLA(2)) during ischemia temporally precedes PMN sequestration in the gut and the appearance of primed PMN in the port al circulation. Therefore, we hypothesized that reperfused gut secrete s platelet activating factor (PAF) via PLA(2) activation that is respo nsible for increased PMN chemotaxis and priming for superoxide (O-2(-) ) generation. Sprague-Dawley rats underwent gut ischemia/reperfusion ( 45 min SMA occlusion/2 hr reperfusion) or sham laparotomy. Distal ileu m was harvested, rinsed with bacteriostatic saline/neomycin, and incub ated for 1 hr at 37 degrees C in RPMI 1640 and the cell-free supernata nt was collected. Normal human PMNs, isolated by plasma-Percoll gradie nts, were pretreated with or without a PAF receptor antagonist (WEB 21 70). Chemotaxis toward gut supernatant was then measured by the agaros e method. Additionally, PMNs were preincubated with or without WEB 217 0 and their O-2(-) release in response to 1 mu M FMLP was measured by the V-max of SOD-inhibitable cytochrome c reduction. Reperfused gut pr oduced a chemotactic index of 2.1 +/- 0.1 compared to 0.2 +/- 0.9 foll owing sham laparotomy (P < 0.05); this was reduced to 0.4 +/- 0.9 with PAF receptor blockade. Similarly, gut I/R supernatant primed PMNs for O-2(-) (P < 0.05) compared to laparotomy, and this effect was abrogat ed by a PAF antagonist. These data suggest that reperfused gut can ela borate PAF which chemoattracts and primes PMNs for O-2(-) generation. (C) 1995 Academic Press, Inc.