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Quantification and kinetics of 25‐hydroxyvitamin D 3 by isotope dilution liquid chromatography/thermospray mass spectrometry
Author(s) -
Vicchio Domenick,
Yergey Alfred,
O'Brien Kimberly,
Allen Lindsay,
Ray Rahul,
Holick Michael
Publication year - 1993
Publication title -
biological mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 1052-9306
DOI - 10.1002/bms.1200220107
Subject(s) - thermospray , chemistry , chromatography , isotope dilution , mass spectrometry , high performance liquid chromatography , isotope , half life , liquid chromatography–mass spectrometry , tandem mass spectrometry , pharmacokinetics , medicine , selected reaction monitoring , physics , quantum mechanics
A liquid chromatography/thermospray mass spectrometry method has been developed and used to measure the plasma levels and half‐life of 25‐hydroxyvitamin D 3 in adults. The mean plasma levels of 25‐hydroxyvitamin D 3 averaged 40 ng ml −1 ( n = 4) in summer and 30 ng ml −1 ( n = 6) in winter. The method was also used to determine the half‐life of serum 5‐hydroxyvitamin D 3 in subjects maintained on either high or low‐fiber diets who had been given an intravenous infusion of (6,19,19‐ 2 H 3 )25‐hydroxyvitamin D 3 sufficient to label 5% of their estimated body pools. The half‐life was determined to be 10.4 days ( n = 4), which is approximately 50% of the currently accepted value of 19 days, determined using radiolabeled methods. This difference may be due to kinetic isotope effects arising as a result of the tritiated compounds being labeled at sites that undergo Cyt‐P 450 ‐catalyzed oxidations.