ER
&

AR
Assay:
Initial
Assumptions
°

ER
and
AR
binding
assays
have
a
long
history
of
use
so
that
a
retrospective
determination
of
relevance
and
reliability
can
be
conducted.
°

Binding
assays
need
only
standardization
of
a
protocol
which
can
be
accomplished
as
part
of
the
QSAR
validation
program.
°

Due
to
the
numerous
variations
in
cell
type,

receptor
and
reporter
constructs,
EPA
should
define
performance
criteria
and
test
chemicals
for
qualification
of
an
assay
by
the
test
sponsor
as
acceptable
for
use
in
the
EDSP.
ER
and
AR
Assay:
The
Reality
°

Despite
a
large
data
base
on
ER
and
AR
binding
assays,
there
is
not
enough
data
on
common
chemicals
across
various
protocols
and
in
various
laboratories
to
permit
a
retrospective
validation.
°

Data
on
the
transcriptional
activation
assays
is
substantially
more
limited
and
falls
far
short
of
adequacy
for
validation.
ER
&AR
Assays:
Where
we
are
now
°

Complete
validation
of
the
ER
rat
uterine
cytosol
assay.
°

Complete
validation
of
the
AR
rat
prostate
cytosol
assay.
°

Investigate
commercial
sources
of
recombinate
human
ER
and
primate
AR.
°

Test
additional
chemicals
with
the
AR
reporter
gene
assay
developed
by
E.

Gray
in
RTP.
°

Wait
for
expert
panel
report
before
deciding
on
further
work.
