ATP‐dependent leukotriene export from mastocytoma cells

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Abstract
The biosynthesis of leukotrienes (LT) C4 and B4 is followed by an export of these mediators into the extracellular space. This transport was characterized using plasma membrane vesicles prepared from mastocytoma cells and identified as an ATP‐dependent primary active process. The apparent Km ‐values were 110 nM for LTC4 and 48 μM for ATP. The transport rate was highest for LTC4, whereas LTD4, LTE4, and N‐acetyl‐LTE4 were transported with relative rates of 31, 12 and 8%, respectively, at a concentation of 10nM. LTB4 transport was also dependent on ATP, LTC4 transport with inhibited by LTD4 receptor antagonists (IC10 = 1.0 μM for MK‐571 and 1.3 μM for LY245769) and by the inhibitor of leukotriene biosynthesis MK‐886 (IC10 = 1.8 μM). The ATP‐dependent export carrier for leukotrienes in leukotriene‐synthesizing cells represents a novel member of the family of ATP‐dependent exit pumps.