A previous
in
vitro
study
by
Vadas
and
Perelman (19)
reported
an
AC/protein
ratio
of
200:1
as
necessary
to
achieve
complete
binding
of
protein
by
AC.
A pH
value
of 3.5
was
used
to
mimic
gastric
conditions,
but
normal
stomach
pH
is
much
lower.
The
protein-AC
mixtures
were
incubated
at 22 C,
a nonphysiologically
relevant
temperature.
Subsequent
findings
from
this
laboratory
have
shown
that
the adsorption
of
protein
onto
AC
increases
progressively
with
temperature (20).
Experiments
at
37 C
not
only
represent
physiological
temperature
but
also
increase
protein
binding
to
AC.
The AC
used
by
Vadas
and
Perelman
was
obtained
by
centrifuging
a commercial
suspension
of
AC
in water.
Even
though
excess
water
was
discarded,
a large
proportion
of
the
mass
of
the
wet
AC
would
be
due
to
water.
If
the amount
of AC
is
measured
via
the volume
of
a suspension,
because
AC
is
not
soluble
and
settles
quickly,
an
aliquot
can
contain
significantly
less
AC.
Although
AC
administered
in
a
clinical
setting
is
in slurry
form,
the
AC
in
the experiments
presented
in
the current
investigation
was
weighed
as
a
dry
powder
so
its
mass
could
be
determined
exactly.
These
factors
may
explain
the
apparent
discrepancy
between
the 200:1 AC/protein
ratio
required
for
complete
adsorption
reported
by
Vadas
and
Perelman
and
the 80:1
ratio
reported
both
here
and
in
a previous
publication (20).