0013.7227/92/1316-3117$0.300/O Endocrinology Copyright 0 1992 by The Endcaine
Vol. 131, No. 6 Printed in U.S.A.
Society
In Vitro Ligand Binding to the Female Rat Brain
of 1*91-Recombinant
Human
Lyn Jakeman’, jennie Mather2, Teresa Woodruff*,3 1Present address: Dept of Neuroscience, Syntex Alto, CA 94303 2Dept Cell Culture R&D, Genentech, Inc. South San Francisco, CA 94060 2~3To whom correspondence should be addressed.
Activin
Research,
A Materials and Methods Materials: Recombinant human activin A (rh-activin A) (mol wt. 28,odO) was expressed and purified as previously described (6). The recombinant molecules were formulated in a buffer of 0.15 M NaCl and 0.05 M Tris pH 7.4. Animals: Adult (60-day) Sprague-Dawley female rats were obtained from Charles Rivers Laboratories (Wilmington, MA). The animals were maintained on a 1410 1ight:dark schedule with constant access to food and water. Animals were sacrificed by CO2 narcosis at 1000 hours. Brains were removed and immediately frozen in an isopentane-dry ice bath. Sections of 20 mm thickness were cut, mounted onto pretreated slides, and stored at -70C until further processed. Iodination of Drug: Rh-activin A was iodinated using commercially available enzymobeads according to manufacturers specifications (BioRad, Hercules, CA). Free iodine was removed using Sephadex G-10 column chromatography (PD-10, Pharmacia Inc., Pitscataway NJ). The specific activities of the preparations were approximately 100 mCi/mg. The bioactivity of the iodinated preparations were not distinguishable from unlabeled material as assessed by FSH release from rat pituitary cells (7). Ligand Binding: Tissue sections were incubated for 3 hours at room temperature in buffer A: DMEM:FlZ (l:l), 20 mM HEPES, 0.05% cytochrome C, 0.3% BSA, 0.01 mg/ml PMSF, 0.01% bacitracin, O.lmg/ml leupeptin. Based upon preliminary association and dissociation experiments (data not shown), slides room temperature were then incubated at
Palo
Abstract Activin has been localized within cells and terminals in the brain. However, little is known about the site of action of this hormone within the brain. In the present study in vitro ligand autoradiography was used to determine the distribution of high affinity binding sites for 1251.rh activin A in rat brain. The highest density of binding sites were concentrated in the amygdala and other forebrain limbic structures. Binding was saturable in selected amygdala nuclei with an apparent Kd of -0.2 nM. 1251rh activin A binds specifically in regions known to contain terminals immunoreactive for this hormone, and also at sites distinct from the location of activin A containing neuronal terminals (e.g. the ventral liibic system). Introduction Activin is a member of the inhibin/TGFb superfamily of multi-action growth factors and modulators. In vitro actions include the regulation of ovarian steroidogenesis, spermatogenesis, neuronal survival, pituitary FSH secretion and hematopoietic cell differentiation (reviewed in 1 and 2). Known targets for in uivo actions in the periphery include the pituitary, gonads, and bone marrow. Activin is also produced within neurons in the brain (3). Subunit protein and mRNA have been localized to cell bodies in the nucleus tractus solitarus and midbrain as well as terminals in hyopothalamic nuclei associated with fluid regulation and oxytocin secretion. In viva central nervous system (CNS) studies show that infusion of exogenous
Table 1: Relative Regions are listed D refer to sections from moderate (+)
Density of Binding Sites in Rat Brain Regions. in functional groups from rostra1 to caudal. Ain Figure 1. Density is indicated qualitative!y to most intense (++++).
activin can modulate oxytocin secretion (4), increase water intake, increase urine output and decrease urine osmolarity (5). In the present study, we have used 1251.rh activin A to identify specific binding sites for activin A in the brain. We have mapped where high affinity binding occurs in the brain as a direct measure of where both endogenous and exogenous activin may exert actions on CNS function.
Received
in
Iowa
City
office
7/g/92
3117
The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 26 November 2015. at 17:27 For personal use only. No other uses without permission. . All rights reserved.
RAPID
3118 overrught A with
COMMUNICATIONS
m the same buffer contammg lo-54 pM 1251-rh actlvm 14-25 nM excess rh actlvm A to defme non speclflc
background mcubated
For saturation curves, m 0 01 to 2 0 nM radlohgand
competitor
The slides were
subsequently
1 set 1, PBS [2 x 10 mm], glutaraldehyde) allowed to dry days
X-ray
adlacent sectlons with or without washed
and aldehyde
films
were
exammed
systems (Amersham), and modiflcatlon of the program
A [2 x
formalm,
2%
[4 x 1 set 1; and finally to Hyperfllm for 7-14
by RAS-3000
saturation LIGAND
m buffer
fix (10%
[lo mm]; rinsed m water Dry sbdes were exposed
were excess
curves (8)
image
analysis
analyzed
usmg
a
Results These distribution
results
represent
of binding
a descriptive
sites in 8 adult
female
analysis rat brains,
of the examined
in 3 separate experiments. were sectioned in a coronal
For anatomical localization, brains plane and compared with the brain
atlas of I’awinos
(9). The findings
and Watson
are presented
as a
list of brain regions with incubation of sections in lo-54
displaceable pM 1251-rh
1 shows binding of 1251-rh sections from five rostrotaudal
activin A to representative brain levels. The areas with the highest
density
of binding
of the rostra1
sites, indicated
caudate
putamen
in red, are identified and nucleus
bed nucleus of the stria terminalis lC), ventromedial hypothalamus (fig
1E).
Competition
amygdala listed
is shown in Table
throughout choroid
plexus Binding
analysis
from
isotherm binding activin
of binding
1, moderate, and
from medial was saturable A. Scatchard amygdala
(Kd=0.15+/~.01). concentration
Figure
1: A-D
density
(red)
variable,
intense
binding
of 2 rats.
of the caudal
to the functional
but
analysis
binding
groups was
was present
seen in the
by equilibrium
saturation
A representative
saturation
revealed
binding
to a single
of the stria terminalis
(Kd=0.23+/-O.Ol),
and
class of
(Kd=0.24+/JI.02), caudal
amygdala
Specific binding at or below the equilibrium represented &O-70% of total binding.
Dlstributlon
Sttes m Coronal Rat Bram regions of low (blue-green), homogeneous,
(fig lA),
amygdala is shown in Fig 2. Specific over the range of 0.01-2.0 nM 125l-rh
sites in the bed nucleus medial
at the level
(CP, fig IA-C). affinity was determined serial sections
at the level
accumbens
(fig IB), medial amygdala (fig (fig 1D) and caudal amygdala
in fig 1F. In addition
the cortex
binding following activin A (Table 1). Fig
blnding as Illustrated
of Total Sectlons moderate sites
1251-rh
actlvin
A Binding
Pseudocolor Images reflect (yellow-orange), and high
Non-speclflc at the caudal amygdala
bIndIng was level m F
The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 26 November 2015. at 17:27 For personal use only. No other uses without permission. . All rights reserved.
En& * 1992 ~oll:~,.so6
RAPID
COMMUNICATIONS
subunits
have
Discussion
References
The rnRNA been identified
and protein in the brain
for an activin
receptor
the brain.
The presence
regulation
of pituitary be involved
also
responses
in brain
(3).
of such activin
response. in
Our
of these
bound
1251-rh
activin
nucleus
and the anterior
involved
in the release
is known
to regulate
activin results
This region functions,
oxytocin
throughout
the ventral Further
binding
corresponds
will
nucleus.
and regions
These regions nucleus
are
which
input
from
it may what
kinase
activin
possible
exert
proportion receptor,
binding
C., Hsueh,
Chemical
and
family
of protein
hormones.
Exp. med.
Biol. (in press).
3. Roberts,
V., Meunier,
Recent
pathways
Press Norwell
involved
H., et. al.
of the inhibin
Prog. Horm.
H., Plotsky, Proteins regulation
P., Pfeiffer,
C., Meunier,
characterization
Res. 44:1-34.
T., Krummen, L. 1992. Paracrine function by inhibin and activin. Sot.
Vale, W Inhibin/Activin 277 in: Neuroendocrine 4. Plotsky,
A., Campen,
biological
2. Mather, J., Woodruff, regulation of reproductive
P., Rivier,
C., Sawchenko,
in Rat Pituitary of Reproduction.
MA
1990)
S, Vale, W 1988 Inhibin
in the control
P.,
and Brain 269ed SSC Yen,
B in central
of oxytocin
secretion.
neural Nature.
334:615-617. 5. Schwall, R., Jakeman, L., Altar, infusion of activin-A on urine volume the rat. Endocrmol.
C. Effect of hypothalamic and water consumption
in
(submitted)
6. Schwall, R., Schmelzer, C., Matsuzama, E., Mason, A 1989. Multiple actions of recombinant activin A in uioo. Endocrinol. 125:1420-3. 7.
1251.rh activin A. These with high affinity to sites where
or to other
and
hypothalamic
and recieves
determine
to the serine
receptors (e.g. inhibin), as follistatm.
preoptic
secretion
forebrain,
studies
learning
to gustatory dimorphic
The paraventricular
containing fibers also binds suggest that activin A binds
actions.
is described as an visceral effector and
1. Vale, W., Rivier, 1988.
Vale, W. Serono
to hypothalamic
A: the medial
hypothalamic
that activin is the intense
reproduction,
feedback Two sexually
of LH.
in neuronal and the
uncharacterized,
interest
project
brainstem nuclei to provide osmoregulatory brain regions. also
data suggests
Of particular
nuclei
yet its
sites in the brain
activin production, as yet
aggression,
encoding
This report identifies sites for rh activin A in
A binding
additional,
function.
mRNA in the brain,
(10). binding
role of brain-derived balance, oxytocin
ingestion,
Outputs
recently,
identified
binding to regions of the amygdala. integrative nucleus for endocrine mechamsms,
for activin
More
not defined high affinity
supports a paracrine development, water may
encoding
has been
distribution is still saturable and specific
(11).
3119
Krummen,L.,
pituitary
Baldwin,
D., Wilfinger,
cells and assessment
synthesis
and
release
W 1991
of the effects in
In:
znfro.
Culture
of testosterone Greenstein
of
on LH B
(ed)
Neuroendocrine Publishers, London.
Research
Methods.
Harwood
Academic
of this
8.
Rodbard,
D.
Ligand:
a versatile
related
computerized
diverse
proteins
such
Munson,
systems. 9.
P.,
approach
Anal. B&hem.
Paxinos,
of ligand-binding
107:220-239.
G., Watson,
Coordinates.
1980.
for characterization
Academic
C.
1986.
The
Rat Brain
in Stereotaxic
Press, SD. 2nd ed.
10. Mathews, L., Vale, W. 1991. Expression cloning of an activin receptor, a predicted transmembrane serine kinase. Cell 65:1-20. Figure
2: A. Representative
saturation
curve
of 1251~activin
binding in the rat medial amygdala. B. Scatchard in A. Kd=243 pM; Bmax=14.9 fmol/mg protein A
analysis
A
of data
11.
Paxinos,
Forebrain
G. 1985.
The
and Midbrain
Rat
Academic
Nervous
System.
Volume
1.
Press, SD.
z g;;:;
v) g
;I;
iodination
E 0
500
1000
1500
[125I]Activin
COnCentratiOn
B
Acknowledgments:
0
0
= zlo.o man 8.0 : 01 6.0 VE gg 4.0
of 1251-rh
The activin
authors
thank
Lyn
Deguzman
A.
2000 (PM)
006 ii
0.05
!k u c
0.04
ii
0.02
m
n mm
‘m
0.03
n
0.01 0.00
n IL
0.0
4.0
8.0
12.0
Bound
The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 26 November 2015. at 17:27 For personal use only. No other uses without permission. . All rights reserved.
for
Vol. 131, No. 6 Printed in U.S.A.
Society
In Vitro Ligand Binding to the Female Rat Brain
of 1*91-Recombinant
Human
Lyn Jakeman’, jennie Mather2, Teresa Woodruff*,3 1Present address: Dept of Neuroscience, Syntex Alto, CA 94303 2Dept Cell Culture R&D, Genentech, Inc. South San Francisco, CA 94060 2~3To whom correspondence should be addressed.
Activin
Research,
A Materials and Methods Materials: Recombinant human activin A (rh-activin A) (mol wt. 28,odO) was expressed and purified as previously described (6). The recombinant molecules were formulated in a buffer of 0.15 M NaCl and 0.05 M Tris pH 7.4. Animals: Adult (60-day) Sprague-Dawley female rats were obtained from Charles Rivers Laboratories (Wilmington, MA). The animals were maintained on a 1410 1ight:dark schedule with constant access to food and water. Animals were sacrificed by CO2 narcosis at 1000 hours. Brains were removed and immediately frozen in an isopentane-dry ice bath. Sections of 20 mm thickness were cut, mounted onto pretreated slides, and stored at -70C until further processed. Iodination of Drug: Rh-activin A was iodinated using commercially available enzymobeads according to manufacturers specifications (BioRad, Hercules, CA). Free iodine was removed using Sephadex G-10 column chromatography (PD-10, Pharmacia Inc., Pitscataway NJ). The specific activities of the preparations were approximately 100 mCi/mg. The bioactivity of the iodinated preparations were not distinguishable from unlabeled material as assessed by FSH release from rat pituitary cells (7). Ligand Binding: Tissue sections were incubated for 3 hours at room temperature in buffer A: DMEM:FlZ (l:l), 20 mM HEPES, 0.05% cytochrome C, 0.3% BSA, 0.01 mg/ml PMSF, 0.01% bacitracin, O.lmg/ml leupeptin. Based upon preliminary association and dissociation experiments (data not shown), slides room temperature were then incubated at
Palo
Abstract Activin has been localized within cells and terminals in the brain. However, little is known about the site of action of this hormone within the brain. In the present study in vitro ligand autoradiography was used to determine the distribution of high affinity binding sites for 1251.rh activin A in rat brain. The highest density of binding sites were concentrated in the amygdala and other forebrain limbic structures. Binding was saturable in selected amygdala nuclei with an apparent Kd of -0.2 nM. 1251rh activin A binds specifically in regions known to contain terminals immunoreactive for this hormone, and also at sites distinct from the location of activin A containing neuronal terminals (e.g. the ventral liibic system). Introduction Activin is a member of the inhibin/TGFb superfamily of multi-action growth factors and modulators. In vitro actions include the regulation of ovarian steroidogenesis, spermatogenesis, neuronal survival, pituitary FSH secretion and hematopoietic cell differentiation (reviewed in 1 and 2). Known targets for in uivo actions in the periphery include the pituitary, gonads, and bone marrow. Activin is also produced within neurons in the brain (3). Subunit protein and mRNA have been localized to cell bodies in the nucleus tractus solitarus and midbrain as well as terminals in hyopothalamic nuclei associated with fluid regulation and oxytocin secretion. In viva central nervous system (CNS) studies show that infusion of exogenous
Table 1: Relative Regions are listed D refer to sections from moderate (+)
Density of Binding Sites in Rat Brain Regions. in functional groups from rostra1 to caudal. Ain Figure 1. Density is indicated qualitative!y to most intense (++++).
activin can modulate oxytocin secretion (4), increase water intake, increase urine output and decrease urine osmolarity (5). In the present study, we have used 1251.rh activin A to identify specific binding sites for activin A in the brain. We have mapped where high affinity binding occurs in the brain as a direct measure of where both endogenous and exogenous activin may exert actions on CNS function.
Received
in
Iowa
City
office
7/g/92
3117
The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 26 November 2015. at 17:27 For personal use only. No other uses without permission. . All rights reserved.
RAPID
3118 overrught A with
COMMUNICATIONS
m the same buffer contammg lo-54 pM 1251-rh actlvm 14-25 nM excess rh actlvm A to defme non speclflc
background mcubated
For saturation curves, m 0 01 to 2 0 nM radlohgand
competitor
The slides were
subsequently
1 set 1, PBS [2 x 10 mm], glutaraldehyde) allowed to dry days
X-ray
adlacent sectlons with or without washed
and aldehyde
films
were
exammed
systems (Amersham), and modiflcatlon of the program
A [2 x
formalm,
2%
[4 x 1 set 1; and finally to Hyperfllm for 7-14
by RAS-3000
saturation LIGAND
m buffer
fix (10%
[lo mm]; rinsed m water Dry sbdes were exposed
were excess
curves (8)
image
analysis
analyzed
usmg
a
Results These distribution
results
represent
of binding
a descriptive
sites in 8 adult
female
analysis rat brains,
of the examined
in 3 separate experiments. were sectioned in a coronal
For anatomical localization, brains plane and compared with the brain
atlas of I’awinos
(9). The findings
and Watson
are presented
as a
list of brain regions with incubation of sections in lo-54
displaceable pM 1251-rh
1 shows binding of 1251-rh sections from five rostrotaudal
activin A to representative brain levels. The areas with the highest
density
of binding
of the rostra1
sites, indicated
caudate
putamen
in red, are identified and nucleus
bed nucleus of the stria terminalis lC), ventromedial hypothalamus (fig
1E).
Competition
amygdala listed
is shown in Table
throughout choroid
plexus Binding
analysis
from
isotherm binding activin
of binding
1, moderate, and
from medial was saturable A. Scatchard amygdala
(Kd=0.15+/~.01). concentration
Figure
1: A-D
density
(red)
variable,
intense
binding
of 2 rats.
of the caudal
to the functional
but
analysis
binding
groups was
was present
seen in the
by equilibrium
saturation
A representative
saturation
revealed
binding
to a single
of the stria terminalis
(Kd=0.23+/-O.Ol),
and
class of
(Kd=0.24+/JI.02), caudal
amygdala
Specific binding at or below the equilibrium represented &O-70% of total binding.
Dlstributlon
Sttes m Coronal Rat Bram regions of low (blue-green), homogeneous,
(fig lA),
amygdala is shown in Fig 2. Specific over the range of 0.01-2.0 nM 125l-rh
sites in the bed nucleus medial
at the level
(CP, fig IA-C). affinity was determined serial sections
at the level
accumbens
(fig IB), medial amygdala (fig (fig 1D) and caudal amygdala
in fig 1F. In addition
the cortex
binding following activin A (Table 1). Fig
blnding as Illustrated
of Total Sectlons moderate sites
1251-rh
actlvin
A Binding
Pseudocolor Images reflect (yellow-orange), and high
Non-speclflc at the caudal amygdala
bIndIng was level m F
The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 26 November 2015. at 17:27 For personal use only. No other uses without permission. . All rights reserved.
En& * 1992 ~oll:~,.so6
RAPID
COMMUNICATIONS
subunits
have
Discussion
References
The rnRNA been identified
and protein in the brain
for an activin
receptor
the brain.
The presence
regulation
of pituitary be involved
also
responses
in brain
(3).
of such activin
response. in
Our
of these
bound
1251-rh
activin
nucleus
and the anterior
involved
in the release
is known
to regulate
activin results
This region functions,
oxytocin
throughout
the ventral Further
binding
corresponds
will
nucleus.
and regions
These regions nucleus
are
which
input
from
it may what
kinase
activin
possible
exert
proportion receptor,
binding
C., Hsueh,
Chemical
and
family
of protein
hormones.
Exp. med.
Biol. (in press).
3. Roberts,
V., Meunier,
Recent
pathways
Press Norwell
involved
H., et. al.
of the inhibin
Prog. Horm.
H., Plotsky, Proteins regulation
P., Pfeiffer,
C., Meunier,
characterization
Res. 44:1-34.
T., Krummen, L. 1992. Paracrine function by inhibin and activin. Sot.
Vale, W Inhibin/Activin 277 in: Neuroendocrine 4. Plotsky,
A., Campen,
biological
2. Mather, J., Woodruff, regulation of reproductive
P., Rivier,
C., Sawchenko,
in Rat Pituitary of Reproduction.
MA
1990)
S, Vale, W 1988 Inhibin
in the control
P.,
and Brain 269ed SSC Yen,
B in central
of oxytocin
secretion.
neural Nature.
334:615-617. 5. Schwall, R., Jakeman, L., Altar, infusion of activin-A on urine volume the rat. Endocrmol.
C. Effect of hypothalamic and water consumption
in
(submitted)
6. Schwall, R., Schmelzer, C., Matsuzama, E., Mason, A 1989. Multiple actions of recombinant activin A in uioo. Endocrinol. 125:1420-3. 7.
1251.rh activin A. These with high affinity to sites where
or to other
and
hypothalamic
and recieves
determine
to the serine
receptors (e.g. inhibin), as follistatm.
preoptic
secretion
forebrain,
studies
learning
to gustatory dimorphic
The paraventricular
containing fibers also binds suggest that activin A binds
actions.
is described as an visceral effector and
1. Vale, W., Rivier, 1988.
Vale, W. Serono
to hypothalamic
A: the medial
hypothalamic
that activin is the intense
reproduction,
feedback Two sexually
of LH.
in neuronal and the
uncharacterized,
interest
project
brainstem nuclei to provide osmoregulatory brain regions. also
data suggests
Of particular
nuclei
yet its
sites in the brain
activin production, as yet
aggression,
encoding
This report identifies sites for rh activin A in
A binding
additional,
function.
mRNA in the brain,
(10). binding
role of brain-derived balance, oxytocin
ingestion,
Outputs
recently,
identified
binding to regions of the amygdala. integrative nucleus for endocrine mechamsms,
for activin
More
not defined high affinity
supports a paracrine development, water may
encoding
has been
distribution is still saturable and specific
(11).
3119
Krummen,L.,
pituitary
Baldwin,
D., Wilfinger,
cells and assessment
synthesis
and
release
W 1991
of the effects in
In:
znfro.
Culture
of testosterone Greenstein
of
on LH B
(ed)
Neuroendocrine Publishers, London.
Research
Methods.
Harwood
Academic
of this
8.
Rodbard,
D.
Ligand:
a versatile
related
computerized
diverse
proteins
such
Munson,
systems. 9.
P.,
approach
Anal. B&hem.
Paxinos,
of ligand-binding
107:220-239.
G., Watson,
Coordinates.
1980.
for characterization
Academic
C.
1986.
The
Rat Brain
in Stereotaxic
Press, SD. 2nd ed.
10. Mathews, L., Vale, W. 1991. Expression cloning of an activin receptor, a predicted transmembrane serine kinase. Cell 65:1-20. Figure
2: A. Representative
saturation
curve
of 1251~activin
binding in the rat medial amygdala. B. Scatchard in A. Kd=243 pM; Bmax=14.9 fmol/mg protein A
analysis
A
of data
11.
Paxinos,
Forebrain
G. 1985.
The
and Midbrain
Rat
Academic
Nervous
System.
Volume
1.
Press, SD.
z g;;:;
v) g
;I;
iodination
E 0
500
1000
1500
[125I]Activin
COnCentratiOn
B
Acknowledgments:
0
0
= zlo.o man 8.0 : 01 6.0 VE gg 4.0
of 1251-rh
The activin
authors
thank
Lyn
Deguzman
A.
2000 (PM)
006 ii
0.05
!k u c
0.04
ii
0.02
m
n mm
‘m
0.03
n
0.01 0.00
n IL
0.0
4.0
8.0
12.0
Bound
The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 26 November 2015. at 17:27 For personal use only. No other uses without permission. . All rights reserved.
for
