Amplification of arachidonic acid metabolism in rat liver cells (the C-9 cell-line) by tosyl- -phenylalanine chloromethyl ketone and phenylmethyl-sulfonyl fluoride

In the presence of the protease inhibitors phenylmethyl-sulfonyl fluoride and N-tosyl- -phenylalanine chloromethyl ketone, prostacyclin (PGI₂) production by rat liver cells treated with epidermal growth factor, platelet-activating factor, 12-O-tetradecanoylphorbol-13-acetate (TPA), and TPA-type tumor promoters (teleocidin and aplysiatoxin) or 1-oleoyl-2-acetylglycerol is amplified. The PGI2 production stimulated by thapsigargin or exogenous arachidonic acid is not amplified. N-Tosyl- -phenylalanine chloromethyl ketone also amplifies TPA's release of radioactivity from cells isotopically labeled with ³H]arachidonic acid. Indomethacin inhibits the amplification of PGI₂ production but not the release of radioactivity. The presence of the protease inhibitors is not required for the amplification of PGI₂ production. Prior incubation of the cells with these inhibitors, followed by their removal, still results in amplified PGI₂ production by cells subsequently treated with TPA, 1-oleoyl-2-acetylglycerol, or platelet-activating factor but not that stimulated by exogenous arachidonic acid. While phenylmethyl-sulfonyl fluoride's amplification of PGI₂ production by cells treated with TPA was blocked by prior incubation with TPA for 20 h, a similar block of amplification in EGF-treated cells was not observed.