Uptake and metabolism of the cysteinyl leukotrienes C4 and E4 (LTC, and LTE,) were studied in AS-30D hepatoma cell suspensions and compared with rat hepatocytes. The hepatoma cells were deficient in the uptake of ['HILTC, and ['HILTE, but We conclude that ectoenzymes of AS-30D hepatoma cells catalyze the conversion of LTC, to LTE, via LTD4. As compared to hepatocytes, these neoplastic cells have lost the uptake system for cysteinyl leukotrienes and may serve in studies on leukotriene metabolism by cell-surface enzymes.The leukotriene constituents of slow-reacting substance of anaphylaxis LTC,, LTD, and LTE, are rapidly eliminated from blood plasma [I -31. A major portion of intravenously injected cysteinyl leukotrienes is taken up by the liver and excreted into bile in rats [4, 51, mice [6] and guinea-pigs [7]. Hepatocytes as well as kidney cells are characterized by an efficient uptake system for cysteinyl leukotrienes [8, 93. In addition to peptide cleavage of LTC, yielding LTD, and LTE,, the formation of polar metabolites of cysteinyl leukotrienes has been demonstrated [6, 81. Studies on the rnetabo h m of cysteinyl leukotrienes require the discrimination between metabolic reactions catalyzed by ectoenzymes located on the cell surface and intracellular reactions. A discrimination between these two metabolic compartments is possible by the use of cells deficient in the uptake system for cysteinyl leukotrienes. In this report we describe a hepatoma cell line, which is capable of metabolizing extracellular LTC, to LTE4 via LTD4 but shows, in contrast to hepatocytes, no uptake of cysteinyl leukotrienes.