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A rapid oxygen exchange on prostaglandins in plasma represents plasma esterase activity that is inhibited by diethylumbelliferyl phosphate with high affinity
Author(s) -
Brose Stephen A.,
Golovko Mikhail Y.
Publication year - 2012
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.6367
Subject(s) - chemistry , esterase , electrospray ionization , mass spectrometry , metabolism , chromatography , biochemistry , enzyme
RATIONALE Fatty acids (FA) labeled with 18 O at the carboxyl group, including oxidized species (FA 18 O), are a useful, low‐cost, and easy to prepare tool for quantitative and qualitative mass spectrometry (MS) analysis in biological systems. In addition, they are used to trace the fate of FAs in metabolic pathways including FA re‐esterification and lipid remodeling pathways. Although a rapid 18 O exchange on FA 18 O in biological systems has been reported, the mechanism contributing to 18 O exchange has not been fully evaluated. This gap in knowledge limits the use of FA 18 O as a standard for MS and complicates data interpretation for FA metabolism in biological systems. METHODS In the present study we have addressed a number of possible mechanisms for a rapid 18 O exchange on prostaglandin E 2 (PGE 2 ) using rat plasma as a model. High‐performance liquid chromatography coupled with electrospray ionization triple quadrupole MS in the multiple reaction monitoring mode was used for quantification. RESULTS The major mechanism for a rapid 18 O exchange on PGE 2 18 O in rat plasma is PGE 2 processing with esterases, while FA re‐esterification and non‐enzymatic mechanisms do not significantly contribute to this phenomenon. In addition, we report a highly effective inhibition of 18 O exchange with diethylumbelliferyl phosphate that can be used to stabilize FA 18 O in biological samples. CONCLUSIONS These data indicate the necessity to consider esterase activity when FA 18 O are used to study FA metabolism, and the importance of esterase activity inhibition when FA 18 O are used as internal standards for MS analysis in biological systems. In addition, the results provide a rational for the development of new approaches to study esterase activities and affinity towards modified FA. Copyright © 2012 John Wiley & Sons, Ltd.