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A comparison between 14 CO 2 and 13 CO 2 measurements in the respired breath of rats fed sodium acetate
Author(s) -
Ampulski R. S.,
Boggs R. W.
Publication year - 1977
Publication title -
biomedical mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 0306-042X
DOI - 10.1002/bms.1200040208
Subject(s) - chemistry , chromatography , sodium acetate , carbon dioxide , sodium , mass spectrometry , respiration , sodium hydroxide , analytical chemistry (journal) , radiochemistry , botany , organic chemistry , biology
13 CO 2 / 12 CO 2 ratios in the respired breath of rats fed carbon‐13 labeled compounds have been continuously assayed using a mass spectrometer to monitor m / e 44 and 45 in real time. Rats dosed with sodium [1‐ 13 C]acetate were restrained in a specially designed glass metabolism cage. A constant air flow through the cage was continuously monitored for respired carbon dioxide by a commercial analytical organic high resolution mass spectrometer. The mass spectrometer was operated in the peak matching mode while alternately recording the ion intensities of m / e 44 and 45 at a cycle rate of 30 s. The appearance and decay in the breath of excess 13 CO 2 was interpreted for the metabolism of sodium acetate. The minimum dose of label was found to be 1.4 × 10 −4 mol kg −1 . The precision of the mass ratio measurement was ± 1%. Details of the experimental design and limitations of the technique are discussed. In order to compare 13 CO 2 results with an established radiochemical method the rats were also dosed with sodium [1‐ 14 C]acetate. The appearance of 14 CO 2 in the respired breath was followed by bubbling the breath through sodium hydroxide traps with quantitation of radioctivity by means of liquid scintillation counting. A comparison of the rates of respiration of 13 CO 2 and 14 CO 2 showed that the two methods produced comparable results in rats. This finding further substantiates the feasibility of using carbon‐13 labeled compounds in metabolism studies.