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Kupffer cells and other sinusoidal cells were isolated after perfusion and incubation with pronase and collagenase of pieces of liver tissue obtained from organ donors. The resulting cell preparations contained endothelial cells, Kupffer cells and fat-storing cells as well as considerable numbers of leucocytes. Attempts to purify the different sinusoidal cell types by density centrifugation and centrifugal elutriation were successful only for Kupffer cells. Kupffer cells, in contrast to endothelial cells and fat-storing cells, could be kept in maintenance culture for at least 5 days. Cultured Kupffer cells were active in the endocytosis of foreign substances, such as colloidal carbon, latex beads, horseradish peroxidase and bacterial endotoxin. The cultured Kupffer cells synthesized and secreted considerable amounts of prostaglandins PGE2, PGF2 alpha, 6-keto-PGF1 alpha and thromboxane B2. The production of prostaglandins was influenced by the presence of Escherichia coli endotoxin.

Macrophages, isolated from dialysis fluid of three patients with continuous ambulatory peritoneal dialysis (CAPD) at different times during peritonitis were labelled with 14C-arachidonic acid and stimulated with the calcium ionophore A23187. The main metabolites formed by 5-lipoxygenase activity were leukotriene B4 (LTB4) and 5-hydroxy-6, 9, 11, 14-eicosatetraenoic acid (5-HETE). Smaller amounts of cyclooxygenase metabolites were present and also a major compound with an elution time between 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) and thromboxane B2 (TxB2). This substance was isolated, analyzed by GC-MS and identified as 20-hydroxy-leukotriene B4 (20-OH-LTB4). This indicates that human peritoneal macrophages obtained from CAPD not only produce leukotrienes and prostaglandins, but also the omega-hydroxylase product of LTB4, which has been demonstrated to be present in polymorphonuclear leucocytes. The activity of this enzyme was not correlated with the severity of the peritonitis.

Human and rat peritoneal macrophages and rat Kupffer cells were labelled with [1-14C] arachidonic acid and stimulated with the calcium ionophore A23187. The metabolites formed were separated by high pressure liquid chromatography (HPLC). Human peritoneal macrophages formed especially leukotriene B4, 5-hydroxy-6,8,11,14 eicosatetraenoic acid and small amounts of leukotriene C4 and thromboxane B2, 12-hydroxy-5,8,10 heptadecatrienoic acid and 6-keto-prostaglandin F1 alpha, whereas rat peritoneal macrophages mainly produced cyclooxygenase products and in particular thromboxane B2 and 12-hydroxy-5,8,10 heptadecatrienoic acid. Rat Kupffer cells synthesized mainly cyclooxygenase products such as prostaglandin F2 alpha, prostaglandin D2 and prostaglandin E2. These results indicate that the profile of eicosanoids production by macrophages is dependent both on the species and on the tissue from which the macrophage is derived.

The results of these and other experiments mentioned indicate that the actions of glucocorticosteroids on the metabolism of arachidonic acid have different aspects, one of which may be prevailing depending on the tissue studied. The relationship between these different activities is a matter of further investigation in this field.