title: Measurement of stable isotopic enrichment of underivatized acetate by gas chromatography/mass spectrometry: application to in vivo estimation of acetate production.
abstract: In order to assess endogenous and colonic production of acetate, we have developed an assay for determining the isotopic enrichment of plasma acetate using gas chromatography/mass spectrometry (GC/MS). Acidified, deproteinized plasma (200 microliters) was extracted into ethyl ether, and the ether phase was then injected into a gas chromatograph/mass spectrometer fitted with a 30 m x 0.252 mm i.d. capillary column (temperature program 50-245 degrees C at 10 degrees C min-1). Using electron impact GC/MS and selected ion monitoring, peak areas of ions with m/z 60 and 61 (M + 1) were determined. Triplicate extractions of enriched plasma samples (mol.% excess 1.38-1.5%) resulted in a coefficient of variation of 1.6-5.9%. Unenriched plasma samples were found to have an enrichment close to theoretical natural abundance, and analysis of our (1-13C)acetate tracer (99 at.% excess) revealed an ion at m/z 61 and no ion at m/z 60. To verify accuracy, we conducted an in vivo isotope dilution study. In a 1-month-old piglet, fasted for 24 h, changing the rate of a 4 h infusion (mmol h-1) of (1-13C)acetate from 0.141 to 0.282 doubled the isotope enrichment (2.08 x) of the second plateau. The rate of appearance of acetate was 26.0 mumols kg-1 min-1, which is comparable to that reported in fasting sheep.
authors.affiliation: Department of Pediatrics, College of Medicine, Ohio State University, Columbus.
authors.forename: C L
authors.initials: CL
authors.lastname: Kien
authors.forename: D H
authors.initials: DH
authors.lastname: Chang
authors.forename: R D
authors.initials: RD
authors.lastname: Murray
authors.forename: A
authors.initials: A
authors.lastname: Ailabouni
authors.forename: J
authors.initials: J
authors.lastname: Kepner
mesh_terms: D000085:Acetates / Q000032:analysis* / Q000097:blood; D000818:Animals; D001798:Blood Proteins / Q000032:analysis; D002247:Carbon Isotopes; D008401:Gas Chromatography-Mass Spectrometry; D007201:Indicator Dilution Techniques; D013552:Swine; D014462:Ultrafiltration
chemical_list: D000085:Acetates; D001798:Blood Proteins; D002247:Carbon Isotopes