Prostanoid synthesis was investigated in suspensions of isolated mouse hepatocytes and nonparenchymal liver cells. A stable metabolite of thromboxane A2 (TXB2) of prostacyclin (6-keto PGF1 alpha) and one of the prostaglandins (PGF2 alpha) was detected by radio-immuno-assay (RIA). Hepatocytes synthesized mainly TXB2, while smaller amounts of 6-keto PGF1 alpha and PGF2 alpha were detected during 60 min incubation. Homogenization of hepatocytes caused a slight increase of TXB2 production and provoked the synthesis of PGF2 alpha and 6-keto PGF1 alpha. The addition of arachidonate to hepatocytes did not influence prostanoid production at concentrations below 10-5M. Higher concentrations further increased TXB2 production and also increased the synthesis of 6-keto PGF1 alpha and PGF2 alpha. Nonparenchymal cells synthesized all the three types of prostanoids and homogenization of these cells did not result in a marked change. The addition of 10(-7)-10(-5)M arachidonate increased the TXB2, 6-keto PGF1 alpha and PGF2 alpha synthesis in nonparenchymal cells. No further increase was found at higher concentrations.