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Analysis of study length truncation in vitamin A compartmental analysis in human and rats
Author(s) -
Gan Bryan M,
Howe Julie A,
Green Michael H,
Tanumihardjo Sherry A
Publication year - 2012
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.26.1_supplement.646.23
Subject(s) - dilution , truncation (statistics) , isotope dilution , retinyl acetate , chemistry , absorption (acoustics) , absorption rate , fraction (chemistry) , zoology , vitamin , chromatography , mathematics , retinol , biology , biochemistry , materials science , statistics , thermodynamics , physics , mass spectrometry , composite material
Previous studies indicate that isotope dilution tests may not fully reveal total body vitamin A reserves, due to lack of time for dose to fully equilibrate with body stores. A healthy female was given an oral dose of 13 C 4 ‐retinyl acetate (17.5 umol), and blood samples were taken at baseline and over the course of 6 years. Serum retinol was analyzed for 13 C/ 12 C ratio by GC‐C‐IRMS, indicating fraction of dose in the plasma. Fraction of dose data are mathematically modeled using compartmental analysis. Different models were created to simulate a range of study‐lengths and total body reserves (TBR) and other kinetic parameters were calculated for each model. As length of study was increased, TBR was found to increase until it reached a maximum at around 500 days. Disposal rate was found to decrease as length of study increased until it reached a minimum at around 500 days. In agreement with non‐modeled isotope dilution, assumed absorption of dose is directly proportional to amount of total stores, indicating that even with compartmental analysis, accurate assessment of absorption is necessary for proper modeling and TBR calculation. To verify these conclusions with a larger sample size, data from an isotope dilution study in rats is being treated to a similar truncation of study length. These results indicate that there are slower turning over pools of vitamin A that would not be detected with a shorter study length. Grant Funding Source : NIH‐NIDDK 61973