We have reported that U-73122 (1-[6-[[17 beta-3-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-1H-pyrrole- 2,5-dione) an inhibitor of phospholipase C-dependent processes in human polymorphonuclear neutrophils (PMN) and platelets, potently suppresses the responsiveness of suspended PMN and platelets to receptor agonists. We demonstrate here that U-73122 caused a concentration-dependent (10-800 nM) inhibition of N-formyl-methionyl-leucyl-phenylalanine, tumor necrosis factor-alpha (TNF alpha), interleukin-8 and phorbol myristate acetate (PMA)-triggered PMN adhesion on fibronectin, fetal bovine serum or keyhole limpet hemocyanincoated microtiter plates. U-73122 also inhibited PMN adherence to and transmigration through TNF-alpha-activated endothelium (IC50 < 50 nM). Further, U-73122 suppressed interleukin-8, N-formylmethionyl-leucyl-phenylalanine and PMA-stimulated up-regulation of the beta 2-integrin, Mac-1 (CD11b/CD18), on the PMN surface (IC50 < 1.3 microM). U-73122 also caused a time-(15-120 min) and concentration-dependent inhibition (IC50 = 25-100 nM) of the N-formyl-methionyl-leucyl-phenylalanine-, TNF alpha- and PMA-elicited adhesion-dependent, oxidative burst, measured as hydrogen peroxide (H2O2) production, in PMN. The CD18-dependent extracellular release of lactoferrin from PMN activated with these stimuli was also suppressed by U-73122. U-73343 (1-[6-[[17 beta-3- methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-2,5-pyrrolidine dione), a close analog of U-73122, did not affect PMN responsiveness.