Document Detail

Use of acetyl chloride/methanol for assumed selective methylation of plasma nonesterified fatty acids results in significant methylation of esterified fatty acids.
MedLine Citation:
PMID:  8487628     Owner:  NLM     Status:  MEDLINE    
The albumin-bound nonesterified fatty acid pool in plasma, which represents a very small percentage of total plasma fatty acids, has previously been quantitated by a variety of methods. In the present study we determined that the nonesterified fatty acid concentrations in the plasma, quantitated by a popular method using acetyl chloride and methanol which is reported to be specific for methylation of nonesterified fatty acids in the presence of esterified fatty acids (i.e., without prior isolation of the plasma nonesterified fatty acids), were significantly overestimated due to cleavage and methylation of esterified fatty acids. Quantitation of the contaminating fatty acid from the esterified pool demonstrated that the amount of fatty acid cleaved from the esterified pool was enough to exceed the entire mass of nonesterified fatty acids. As an established method for comparison, we isolated nonesterified fatty acids from the plasma by thin-layer chromatography prior to methylation, using a number of simple precautions to limit oxidation. By performing all thin-layer chromatography steps in an atmosphere of nitrogen and by including fatty acid standards in the plasma with 0, 1, 2 or 4 double bonds, we were able to accurately and reproducibly determine the concentration of nonesterified fatty acids in the plasma, including arachidonate. We demonstrated that no oxidation occurred in the thin-layer chromatographic isolation of nonesterified fatty acids and that the coefficients of variation for repeat measurements of the same sample were < 11% using our reference method. Our data indicate that the use of acetyl chloride and methanol for assumed selective methylation of plasma nonesterified fatty acids results in significant methylation of esterified fatty acids.
Y Hallaq; T C Becker; C S Manno; M Laposata
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Lipids     Volume:  28     ISSN:  0024-4201     ISO Abbreviation:  Lipids     Publication Date:  1993 Apr 
Date Detail:
Created Date:  1993-06-09     Completed Date:  1993-06-09     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0060450     Medline TA:  Lipids     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  355-60     Citation Subset:  IM    
Department of Pathology, Massachusetts General Hospital, Harvard Medical School, Boston 02114.
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MeSH Terms
Acetic Acids / chemistry
Chlorides / chemistry
Chromatography, Thin Layer
Fatty Acids / blood*,  chemistry*,  isolation & purification
Fatty Acids, Nonesterified / blood,  chemistry,  isolation & purification
Reference Standards
Reproducibility of Results
Grant Support
Reg. No./Substance:
0/Acetic Acids; 0/Chlorides; 0/Fatty Acids; 0/Fatty Acids, Nonesterified; 67-56-1/Methanol; 75-36-5/acetyl chloride

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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