Lung sequestration in vivo of activated, tritium-labeled rabbit neutrophils

Lung endothelium may be damaged as it interacts with blood neutrophils (PMN) activated by certain bacterial filtrates. N-formyl-methionyl-leucyl-phenylalanine (FMLP) synthetic analog of E. coli endotoxin, causes transient neutropenia and respiratory distress when infused i.v. in rabbits. In this study the authors determined lung, spleen, liver and kidney sequestration of activated PMN. The authors transfused blood from a donor pre-treated with 3 mCi of [3H]-thymidine into test and control (CON) rabbits. PMN were activated with 0.2 ug/Kg of FMLP i.v. Lungs, spleen, liver and kidneys were removed at 2.5 min. and were homogenized. Counts of 100 mg (wet weight) of each organ minus dpm of 100 mg CON were compared. Results were: lung 1242, spleen 448, kidney 235 and liver 209 (n = 10). Values for lung were significantly different from spleen (p < .03), kidney (p < .01) and liver (p < .01). Using the same model, the authors infused FMLP or vehicle and withdrew 6 ml venous blood at intervals. Test and CON values were compared. Each was calculated as percent change from time zero. Results were: at 2.5 min (+ FMLP) - 95% vs (CON) - 1% (p < .0001), at 20 min -69 vs -24 (p < .01), at 40 min -52 vs -19 (p < .01), and at 60 min -27 vs -25 (n.s.). These results indicate that on a per unit wt basis the lung sequestration of FMLP-activated PMN in vivo is significantly greater than that of spleen, kidney or liver and that the same cells sequestered are returned to the peripheral circulating pool