RESUMO
Although some data suggest that macrophages in the reticuloendothelial system (RES) are important sources of thromboxane A2 (TxA2) and prostacyclin (PGI2) during endotoxic shock, we are unaware of data documenting the ability of hepatic macrophages (Kupffer cells) to release either TxA2 or PGI2 when exposed to lipopolysaccharide (endotoxin, LPS). In this study, Kupffer cells were examined for their ability to release prostaglandin E2 (PGE2), TxA2, and PGI2 following stimulation with 0, 1.0, 50.0, and 100.0 micrograms/ml of Escherichia coli LPS. Kupffer cells were obtained from rat livers by enzymatic digestion with 0.05% collagenase followed by enrichment of the macrophage population on the basis of differences in density and adherence among the various cell populations isolated. Based on several criteria (phagocytosis of opsonized sheep erythrocytes, positive staining for esterase and peroxidase, failure to replicate), 95% of adherent cells were Kupffer cells. After 4 days of incubation, cells were stimulated with various doses of LPS for 4 and 8 hr. Prostanoid concentrations in culture supernatants were determined by radioimmunoassay. Increasing doses of LPS significantly (P less than 0.001) increased the concentration of immunoreactive PGE2 (iPGE2) and iTxB2 (the stable metabolite of TxA2). The concentration of i6-keto-PFG1 alpha (stable metabolite of PGI2) increased following stimulation with 1.0 microgram/ml of LPS, but declined as the dose of LPS was increased. The results provide evidence that endotoxin-activated Kupffer cells, like other macrophage populations, release several metabolites of arachidonic acid. Kupffer cell-derived prostanoids, particularly TxA2, may be important mediators of some of the pathophysiologic manifestations of acute endotoxemia.
