A stable isotope method for the simultaneous measurement of vitamin K1 (phylloquinone) kinetics and absorption.
OBJECTIVE
To measure uptake and disposal kinetics and absolute absorption of vitamin K(1) using two stable isotope-labelled forms of vitamin K(1).


METHODS
Ten subjects (nine women and one man) aged between 22 and 31 years, with a mean (+/-standard deviation) body mass index of 22.5+/-2.4 kg/m(2). Subjects took capsules containing 3 microg of methyl-(13)C vitamin K(1), three times a day for six days to reach a steady state for plasma vitamin K(1) isotopic enrichment. On day seven, subjects were given an intravenous dose of Konakion MM to measure disposal kinetics and at the same time, a capsule containing 4 microg of ring-D(4) vitamin K(1) to measure absorption. Plasma vitamin K(1) concentration was measured by high-performance liquid chromatography and isotopic composition by gas chromatography mass spectrometry.


RESULTS
The disposal kinetics of the intravenous dose of vitamin K(1) were resolved into two exponentials with half-times of 0.22 (+/-0.14) and 2.66 (+/-1.69) h. Absorption of oral, deuterated vitamin K(1) was 13 (+/-9)%.


CONCLUSIONS
Two-compartmental kinetic parameters observed in this study are similar to those obtained previously using radioactive tracers, but there may be additional slow-turnover body pools acting as stores of vitamin K(1). The kinetic parameters determined from the intravenous dose allowed determination of the absolute absorption of vitamin K(1) from a bolus oral dose.
MRC Human Nutrition Research, Elsie Widdowson Laboratory, Cambridge, UK. kerry.jones@mrc-hnr.cam.ac.uk
K S
KS
Jones
L J C
LJ
Bluck
L Y
LY
Wang
W A
WA
Coward
D000042:Absorption; D000284:Administration, Oral; D000328:Adult; D019540:Area Under Curve; D001779:Blood Coagulation Factors / Q000008:administration & dosage* / Q000378:metabolism / Q000493:pharmacokinetics*; D002247:Carbon Isotopes; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D003903:Deuterium; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods; D006801:Humans; D007275:Injections, Intravenous; D007553:Isotope Labeling; D008297:Male; D010837:Vitamin K 1 / Q000008:administration & dosage* / Q000097:blood / Q000493:pharmacokinetics*; D055815:Young Adult
D001779:Blood Coagulation Factors; D002247:Carbon Isotopes; D010837:Vitamin K 1; D003903:Deuterium