Identification of the major endogenous leukotriene metabolite in the bile of rats as N-acetyl leukotriene E4.
Mercapturic acid formation, an established pathway in the detoxication of xenobiotics, is demonstrated for cysteinyl leukotrienes generated in rats in vivo after endotoxin treatment. The mercapturate N-acetyl-leukotriene E4 (N-acetyl-LTE4) represented a major metabolite eliminated into bile after injection of [3H]LTC4 as shown by cochromatography with synthetic N-acetyl-LTE4 in four different HPLC solvent systems. The identity of endogenous N-acetyl-LTE4 elicited by endotoxin in vivo was additionally verified by enzymatic deacetylation followed by chemical N-acetylation. The deacetylation was catalyzed by penicillin amidase. Endogenous cysteinyl leukotrienes were quantified by radioimmunoassay after HPLC separation. A N-acetyl-LTE4 concentration of 80 nmol/l was determined in bile collected between 30 and 60 min after endotoxin injection. Under this condition, other cysteinyl leukotrienes detected in bile by radioimmunoassay amounted to less than 5% of N-acetyl-LTE4. The mercapturic acid pathway, leading from the glutathione conjugate LTC4 to N-acetyl-LTE4, thus plays an important role in the deactivation and elimination of these potent endogenous mediators.
D000818:Animals; D001646:Bile / Q000187:drug effects / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D004731:Endotoxins / Q000494:pharmacology; D005260:Female; D007700:Kinetics; D017999:Leukotriene E4 / Q000031:analogs & derivatives*; D011863:Radioimmunoassay / Q000379:methods; D011865:Radioisotope Dilution Technique; D051381:Rats; D011919:Rats, Inbred Strains; D013189:SRS-A / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism; D014316:Tritium
D004731:Endotoxins; D013189:SRS-A; D014316:Tritium; D017999:Leukotriene E4; C047630:N-acetylleukotriene E4