Expression of adhesion molecules on circulating PMN during hyperdynamic endotoxemia.

In a porcine model of hyperdynamic endotoxemia, we studied the numerical expression of L-selectin and beta 2-integrins on circulating polymorphonuclear leukocytes (PMN). Functional changes of beta 2-integrins were determined by the adhesion of PMN to C3-coated zymosan particles. Anesthesized pigs received a continuous infusion of Salmonella abortus-equi endotoxin (5 micrograms.kg body wt-1.h-1) for 270 min (endotoxin group; n = 7). A control group received 0.9% NaCl (n = 6). L-selectin had decreased 30 min after the induction of endotoxemia [59.1 +/- 11.9 vs. 91.6 +/- 15.5 relative fluorescence units (RFU) at baseline; P < 0.05], reaching minimal values after 150 min (23.9 +/- 3.9 RFU in endotoxin group vs. 95.2 +/- 30.4 RFU in control group; P < 0.05). PMN adhesion to C3-coated zymosan increased at 30 min (41.3 +/- 9.9% in endotoxin group vs. 2.4 +/- 1.1% in control group; P < 0.05) and remained significantly elevated thereafter. In contrast to the rapid shedding of L-selectin and functional upregulation of beta 2-integrins, the numerical expression of beta 2-integrins remained unchanged until 60 min (44.8 +/- 2.8 vs. 32.2 +/- 1.7 RFU at baseline; P < 0.05); compared with the control group, significantly elevated values were observed 150 min after the start of endotoxin (48.9 +/- 2.4 RFU in endotoxin group vs. 36.5 +/- 2.7 RFU in control group; P < 0.05). We conclude that numerical and functional expressions of beta 2-integrins are dissociated during endotoxemia. Although upregulation of beta 2-integrins might render PMN more adhesive to the vascular endothelium, the presence of activated PMN in the circulation suggests that low expression of L-selectin might impede adhesion.