We compared the therapeutic effects of anti-leukocyte adhesion molecule antibodies (mAbs), a nitric oxide (NO) synthase inhibitor (monomethyl-L-arginine, NMLA), and methylprednisolone (MP) on experimental endotoxin-induced shock in mice. Lipopolysaccharide (LPS, 30 mg/kg) was administered to ICR mice intraperitoneally, While 1 mg/kg mAb, 5-20 mg/kg NMLA, or 30 mg/kg MP was administered intravenously. The placebo group received phosphate-buffered saline. The survival rate of the placebo group 48 h after LPS injection was 36%. The administration of anti-CD11a, anti-CD18, anti-lectin cell adhesion molecule-1 (anti-LECAM-1), and MP increased the survival rate to 70, 62, 64, and 100%, respectively; however, NMLA had no significant effect. A FACS analysis revealed that the CD18 expression of granulocytes increased 12-fold within 30 min after LPS administration. MP significantly suppressed its expression. The plasma level of nitrate/nitrite increased from 20 to 260 and 1000 microM 4 and 16 h, respectively, 20 mg/kg NMLA abolished NO production at 4 h, while MP inhibited it for up to 16 h. The hepatic malondialdehyde level increased from 0.50 to 2.46 nmol/mg protein at 4 h. Administration of anti-CD18 and MP reduced the level to 1.80 and 1.41 nmol/mg protein, respectively, whereas NMLA did not affect it. The mAbs and MP were concluded to be useful agents for endotoxin shock. The abolition of NO production had little influence on the hepatic cellular injury associated with endotoxemia.