The effects of interleukin-1 (IL-1) and arachidonic acid metabolites, prostaglandin (PG) E1, leukotriene (LT) B4 and LTC4, on the amount of platelet activating factor (PAF) produced and released by mouse hepatic sinusoidal endothelial cells were investigated. When hepatic sinusoidal endothelial cells were incubated with 1 microgram/mL of calcium ionophore (CaI) A23187, PAF production increased until 20 min after the start of incubation, but when the cells were incubated with PGE1 and CaI A23187, PAF production was significantly suppressed. On the other hand, when hepatic sinusoidal endothelial cells were incubated with IL-1 beta, LTB4 or LTC4 alone, PAF production significantly increased compared with that of the cells incubated without these substances. However, when the cells were incubated with PGE1 alone or with IL-1 beta, LTB4 or LTC4 and CaI A23187, these effects were not observed. These results indicated that PAF produced by hepatic sinusoidal endothelial cells is affected by IL-1 and arachidonic acid metabolites, suggesting that immune and inflammatory reactions in these cells may be regulated by chemical mediators produced by the cells themselves.