ATP‐dependent leukotriene export from mastocytoma cells

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 K_m ‐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.