Evidence of in-vivo omega-oxidation of peptide leukotrienes in the rat: biliary excretion of 20-CO2H N-acetyl LTE4.
In a previous study in our laboratory it was observed that after [3H] LTC4 administration (luCi/kg i.v.) to the anesthetized rat, significant amounts of injected radioactivity (approximately 25%) were associated with previously unidentified biliary polar metabolite(s). In the present study we describe the isolation and characterization of the predominant polar metabolite. Rats were injected with synthetic LTC4 (20 microgram/kg i.v.) and bile collected over 30 min. After extraction and purification (2 step RP-HPLC procedure), the retention time of the metabolite was compared (plus coinjections) and found to be identical with synthetic 20-CO2H N-Ac LTE4 in two RP-HPLC systems. Also, the UV spectrum of the biologically derived metabolite was compared and found identical to the synthetic material, giving a characteristic conjugated triene absorption in the UV with a max of 281 nm and shoulders at 270 and 290 nm. Further, the trimethyl ester derivative of the metabolite showed identical chromatographic behaviors in 2 reverse and 2 normal phase HPLC systems compared with synthetic 20-CO2H N-Ac LTE4 trimethyl ester. We conclude omega-oxidation of peptide leukotrienes occurs in the rat and that 20-CO2H N-Ac LTE4 is an in vivo product of LTC4 metabolism.
Foster
A
A
Department of Pharmacology and Medicinal Chemistry, Merck Frosst Canada Inc., Pointe Claire-Dorval, Québec.
Fitzsimmons
B
B
Rokach
J
J
Letts
G
G
D000818:Animals; D001646:Bile / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D017999:Leukotriene E4 / Q000031:analogs & derivatives; D008297:Male; D010084:Oxidation-Reduction; D051381:Rats; D013189:SRS-A / Q000031:analogs & derivatives* / Q000378:metabolism*; D012995:Solubility; D013056:Spectrophotometry, Ultraviolet
D013189:SRS-A; C054177:20-carboxy-N-acetylleukotriene E4; D017999:Leukotriene E4