Vitamin K1 metabolism and the production of des-carboxy prothrombin and
protein C in the term and premature neonate
EG Bovill, RF Soll, M Lynch, F Bhushan, M Landesman, M Freije, W Church, T McAuliffe, K Davidson and J Sadowski
Department of Pathology, University of Vermont College of Medicine,
Burlington.
This study investigated the incidences of undercarboxylated (protein
induced by vitamin K absence: PIVKA) prothrombin and protein C in 496
neonates across a wide range of gestational ages. These findings are
related to vitamin K1 levels (an indicator of cofactor availability) and
vitamin K1 epoxide levels (a measure of the efficiency of the hepatic
vitamin K cycle). PIVKA protein C was present in at least trace amounts in
27% of infants; whereas, PIVKA prothrombin was present in 7% of infants.
PIVKA prothrombin and protein C were present at high plasma concentrations
in 2% to 3% of term and preterm neonates and both PIVKA protein C and
prothrombin increased with gestational age. Despite elevated plasma
concentrations of PIVKA protein C and diminished levels of normally
carboxylated protein C, clinical thrombosis was not observed. The mean (+/-
SD) vitamin K1 level in the study population was 0.009 +/- 0.02 nmol/L
(adult reference interval: 0.3 to 2.6 nmol/L) with no clear relationship
between vitamin K1 levels and production of PIVKA protein C or prothrombin.
By comparison with adults, the epoxide form of the vitamin comprised an
abnormally high proportion of total vitamin K1; this suggests possible
inefficiencies in hepatic reductase cycling.
Volume 81,
Issue 1,
pp. 77-83,
01/01/1993
Copyright © 1993 by The American Society of Hematology
