We first studied the production of interleukin 1 (IL1) and platelet-activating factor (PAF) by mouse hepatic sinusoidal endothelial cells and then the effect of Lipo-prostaglandin E1 (Lipo-PGE1) on IL1 and PAF production by these cells. The incubation of mouse hepatic sinusoidal endothelial cells with lipopolysaccharide (LPS) or calcium-ionophore (CaI) A23187 resulted in a concentration-dependent production of IL1 and PAF. However, Lipo-PGE1 dose-dependently decreased the LPS- or CaI A23187-induced production of IL1 and PAF. These results suggested that Lipo-PGE1 acts on hepatic sinusoidal endothelial cells to decrease the production of IL1 and PAF, thereby ameliorating inflammatory reactions in the liver.