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N Colman and V Herbert
The current study presents evidence that all human serum contains a class
of high-affinity folate binders (KA=2.8 X10(10 liters/mole), which migrate
as a single peak on gel filtration. Failure of previous studies to detect
this characteristic in all but a minority of subjects is attributable to
its variable, often total, saturation. Direct measurement of the total
folate binding capacity (TFBC) has been made possible by dissociation of
endogenous folate-binder complexes at acid pH, removal of free folate by
coated charcoal, and radiofolate tagging. This procedure does not appear to
significantly denature the binders, which release and rebind similar
quantities of 3H-PGA. In 20 normal subjects, TFBC ranged from 100 to 325
pg/ml (mean+/-SE = 174+/-16), and was always at least 33% saturated. In
three clinical conditions, all associated with elevated unsaturated folate
binding capacity, three different patterns emerged when TFBC was also
measured. Uremic subjects had significantly elevated mean TFBC with normal
saturation. In cirrhotic subjects, mean TFBC approximated normal, but
saturation was significantly decreased. In pregnancy, two groups were seen:
one with increased TFBC and the other with a normal TFBC, some of whom had
decreased saturation. Lactobacillus casei serum folate level was about 30
times greater than the TFBC; there was no correlation between the two
measurements.
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| Copyright © 1976 by American Society of Hematology Online ISSN: 1528-0020 | |||||||||
