We investigated the secretory profiles of prostanoids in two types of nonparenchymal cell from the rat liver, sinusoidal endothelial cells and Kupffer cells, in primary culture both under basal conditions and after stimulation with adenine nucleotides. Prostaglandin (PG) Ez was the main prostanoid secreted by both types of hepatic nonparenchymal cell in the basal and adenosine triphosphate (ATPI-stimulated states. Time-and concentration-dependent effects of ATP-mediated PGE2 secretion were noted in sinusoidal endothelial cells, whereas the profile of the relative potencies of individual nucleotides was consistent with the presence of PZy and PI purinergic receptoi-s. In Kupffer cells, the regulation of prostanoid secretion by adenine nucleotides was essentially the same its that in sinusoidal endothelial cells except that adenosine did not stimulate prostanoid secretion and that. prostanoid secretion differed somewhat; Kupffer cells secreted relatively more PGFz, and less 6-keto-PGF1, than sinusoidal endothelial cells in the presence of ATP, suggesting the presence of only PBy receptors. In summary, PGEz is the main prostanoid secreted by hepatic nonparenchymal cells and its secretion may be stimulated by adenine nucleotides and adenosine. (HEPATOLOGY 1995;21:1713-1718.