Generation of leukotrienes and hydroxyeicosatetraenoic acids in peritoneal macrophages of tumor-bearing mice.

To examine the potential role of lipoxygenase products in the pathophysiology observed after experimental tumor implantation, we examined the generation of leukotrienes (LTs) and hydroxyeicosatetraenoic acids (HETEs) in peritoneal macrophages. C57BL/6 mice were given subcutaneous inoculations of B16 melanoma cells, and peritoneal macrophages were isolated various days after the inoculation. Macrophages were incubated for 1 h at 37 degrees C in serum-free RPM11640 containing 10 microM calcium ionophore A23187, 10 microM exogenous arachidonic acid (AA), 5 mM cysteine hydrochloride and 1 mM reduced glutathione. LTs and HETEs were separately extracted, passed through Sep-Pak cartridges, then identified and quantitated with a HPLC system using UV absorbance. The B16 melanoma-cell-treated/untreated macrophages were found to produce substantial amounts of 15-HETE, 12-HETE and 5-HETE and LTC4 by enzymatic mechanisms. Thus, when determined under various conditions, the production of HETEs was dependent on substrate-concentration, incubation-time and cell-number. The production of LTC4 was dependent on incubation-time and cell number but not substrate-concentration, indicating utilization of endogenous AA stores. Of these products, 12-HETE and LTC4 showed a significant increase on the fourth day after the tumor cell inoculation and returned to the control level by the 11th day after the same treatment. These results suggest that in vivo tumor cell implantation may induce a transient increase of 12-HETE and LTC4 production in macrophages.