Total body phylloquinone and its turnover in human subjects at two levels of vitamin K intake.
The aims of this study were to determine the total body phylloquinone and its metabolic turnover in human subjects using a tracer dose of [5-H3]phylloquinone containing 4 MBq/mmol. Seven subjects aged 22 to 49 years were given 0.3 microg isotopic phylloquinone intravenously on a control diet (75 microg phylloquinone/d) and blood, urine and faeces were sampled periodically for 6 d. Five of these subjects were studied a second time after 3-8 weeks on a low-vitamin K diet (8 microg/d). The changes in the radioactivity of plasma phylloquinone with time were analysed by the method of residuals and fitted to a curve composed of two exponential components. The size of the exchangeable body pool was calculated by isotope dilution. Plasma phylloquinone levels fell during vitamin K restriction but the vitamin K-dependent coagulation factors did not change. After injection the first exponential decay curve t1/2 was 1.0 (sd 0.47) h in the subjects on the control diet and 0.49 (sd 0.27) h after vitamin K restriction. On the control diet, the second exponential t1/2 was 27.6 (sd 124) h that did not change on the low-vitamin K diet ( (sd 13.5) h). These results indicate that the turnover time for phylloquinone in human subjects is about 1.5 d. Urinary excretion of 3H-metabolites ranged from 30 % of the administered dose on the control diet to 38 % on the restricted diet and had the same turnover rate as the second component of the plasma decay curves. The exchangeable body pool of phylloquinone declined from about 1.0 microg/kg before restriction to lower values after vitamin K restriction. The faecal excretion of phylloquinone and its metabolites fell from 32 % of the administered dose on the control diet to 13 % on the restricted diet.
Olson
Robert E
RE
Department of Pediatrics, College of Medicine, University of South Florida, Tampa, USA. rolson@hsc.usf.edu
Chao
Jean
J
Graham
Donna
D
Bates
Margaret W
MW
Lewis
Jessica H
JH
D000328:Adult; D001779:Blood Coagulation Factors / Q000378:metabolism; D001835:Body Weight; D004032:Diet; D004334:Drug Administration Schedule; D005243:Feces / Q000737:chemistry; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011517:Prothrombin Time; D014316:Tritium; D010837:Vitamin K 1 / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*
D001779:Blood Coagulation Factors; D014316:Tritium; D010837:Vitamin K 1