AbstractThe in vitro incubation of cells from turpentine‐induced rat myeloid hyperplastic marrow and peritoneal monocyte/macrophage with14C‐arachidonic acid resulted in the incorporation of the radiolabel into the particulate phospholipids. Challenge of the radiolabeled cells with a highly purified type I CSF (CSF I) from human pancreatic carcinoma cells in continuous culture resulted in the hydrolysis and release of the14C‐arachidonic acid from the cellular phospholipids. The simultaneous challenge of the prelabeled cells with CSF‐I and its specific antibody (anti‐CSF‐I antibody) inhibited the CSF‐I induced hydrolysis of14C‐arachidonic acid from the cells. These results confer a specificity on the CSF‐I induced release of arachidonic acid from the cellular phospholipids. Our data also demonstrated that the14C‐arachidonic acid released from the cellular phospholipids was further transformed into products of the cyclooxygenation and lipoxygenation pathways by cellular enzyme systems in both populations of cells. Interestingly, our data also indicate that the challenge of the granulocytic hyperplastic marrow cells and the monocyte/macrophage cells with purified CSF‐I resulted in a higher generation of lipoxygenase products in the predominantly granulocytic cell population than in the population rich in monocyte/macrophage cells. The biological significance of this observation remains to be further explored. Thus, the CSF‐I‐induced release of cellular arachidonic acid explains, at least in part, the presence of prostaglandins and other metabolites of arachidonic acid that are found in the media of hemopoietic cells incubated with a va
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