Endothelial cell (EC) activation plays a key role in the inflammatory response by promoting the margination of leukocytes in inflamed loci. Augmented leukocyte margination to activated EC is mediated by the increased display of leukocyte adhesion molecules on EC surface membranes. The biocompatibility of synthetic oxygen-transport fluids is intimately linked to EC function, since one of the first tissues encountered by such fluids is the vascular endothelium. We investigated the effect of one such agent, a phospholipid-based perfluorocarbon emulsion containing 90% w/v perfluorooctyl bromide (perflubron, PFOB) on EC activation. Human umbilical vein EC (HUVEC) were activated by 5 U/ml interleukin-1 (IL-1), 20 U/ml tumor necrosis factor (TNF), or 50 ng/ml E coli endotoxin (LPS) in the presence or absence of up to 20%, w/v perflubron. HUVEC activation was monitored by the extent of up-regulation of expression of intercellular adhesion molecule-1 (ICAM) and endothelial-leukocyte adhesion molecule-1 (ELAM). Exposure of HUVEC to perflubron did not alter the upregulation of ICAM or ELAM in response to IL-1 or TNF (n = 20). However, at 10% perflubron ICAM upregulation in response to LPS was inhibited by 95 +/- 6% (n = 9; p < .05). ELAM expression was similarly affected. The concentration of perflubron required to diminish LPS-induced up-regulation by 50% was 6.0 +/- 0.6% (n = 3). The inhibitory effect of 10% perflubron was overcome by > 1 microgram/ml LPS (n = 3) and the inhibitory effect was attenuated by adding perflubron to the cultures after LPS. In agreement with the above, additional experiments showed that incubation of LPS with perflubron prevented LPS-induced stimulation of TNF synthesis by a murine macrophage (RAW) cell line (n = 3). We conclude: 1) perflubron neither activates HUVEC nor interferes with HUVEC activation by IL-1 or TNF, 2) perflubron prevented HUVEC activation by LPS in a dose and time-dependent manner, 3) perflubron prevented LPS-induced activation of more than one cell line. Taken together, the data suggest that perflubron may bind and sequester limited concentrations of LPS. Whether this property of perflubron also occurs upon in vivo infusion and whether it might be clinically useful in preventing some of the adverse effects of endotoxemia are unknown.