Human mononuclear phagocytes from different anatomical sites differ in their capacity to metabolize arachidonic acid

Human mononuclear phagocytes have the capacity to metabolize arachidonic acid (AA) into prostaglandin (PG) endowed with potent activities in immune responses and inflammatory processes. We have evaluated AA metabolism in human mononuclear phagocytes harvested from different anatomical sites (blood monocytes, macrophages from milk, peritoneal activity and alveolar spaces). At thin layer radiochromatography, the AA metabolites mainly present were PGE₂, TxB₂ and, only in bronchoalveolar macrophages, a peak comigrating with PGD₂. No appreciable levels of 6-keto-PGF (1α) were observed. These data were confirmed using specific radioimmunoassays for TxB₂, PGE₂, and 6-keto-PGF(1α). Blood monocytes and bronchoalveolar macrophages were the poorest producers of PG, with the possible exception of PGD₂ in bronchoalveolar macrophages. The high amounts of TxB₂ and PGE₂ produced by milk macrophages could contribute to the levels of PG in human milk. Thus, human mononuclear phagocytes obtained from diverse anatomical sites are considerably heterogeneous in terms of AA metabolism.