BIOLOGY
OF
REPRODUCTION
20,
Estrogen
1187-1193
(1979)
Feedback
and the
Effect
in the Pig:
of Prenatal
F. ELSAESSER
institut
and
f#{252}r
Tierzucbt
Differentiation
Treatment
N. PAR VIZI
und
Mariensee,
Tierverhalten,
3057
Federal
Sexual
Testosterone
FAL,
Neustadt
Republic
1,
of Germany
ABSTRACT
studied
the stimulatory
estrogen
feedback
on LH release
in newborn
(6-day-old)
and prepubertal
(160-day-old)
male and female Landrace
pigs and the effect
of exposure
to testosterone
in
fetal life on sexual differentiation
of the stimulatory
estrogen
feedback.
In newborn
gonadectomized
male pigs neither
60 nor 600 pg estradiol
benzoate
(EB)/kg
BW
i.m. had an effect on the level of LH in the plasma for up to 120 h following
treatment.
In female
neonates
the plasma
concentrations
of LHwere
significantly
(P<0.05)
suppressed
only at 24 h
after 600 pg EB/kg
BW. Gonadectomized
prepubertal
male pigs responded
to 60 pg EB/kg BW with
a significant
(P<0.01)
decrease
of plasma
LH at 24 h and a return
to pretreatment
levels at 72 h
in the face of still elevated
estradiol-17
levels. Prepubertal
guts responded
to 60 pg EB/kg
BW with
a surge of LH 48-60
h following
treatment.
The stimulatory
estrogen
feedback
was significantly
(P<0.05)
impaired
in females
of the same age that had been exposed
to testosterone-propionate
(TP) via their mother
(i.m. injections
on 3 occasions
separated
by 2 day intervals,
5 mg/kg
BW)
starting
on Day 30, 50 or 70 of fetal life. The number
of gilts that had ovulated
by 250 days was
reduced
and the weight
of the ovaries
and the uterus
was signifcantly
(P<0.01
and P<0.001,
respectively)
depressed.
TP treatment
of sows starting
on Day 90 or 106 of pregnancy
had no
effect
on the functioning
of the stimulatory
estrogen
feedback
mechanism
or the ovaries of their
female offspring.
We conclude
that the stimulatory
estrogen
feedback
mechanism
of the female pig gradually
matures
and suggest that with respect
to the effect of prenatal
or neonatal
testosterone
treatment
on the estrogen feedback
the pig is similar to the rat, guinea pig and sheep, but different
from the
rhesus monkey.
The observed
sexual dimorphism
in the LH response
to estradiol
benzoate
might
be quantitative
rather than qualitative.
We
INTRODUCTION
The
concept
of
sexual
control
of luteinizing
androgens
during
or neonatal
(Barraclough,
a
hormone
critical
(LH)
period
life
seems to be valid
1966;
Gorski,
1973),
feedback
mechanism
(Karsch
et al.,
The
stimulatory
rodents
the
the
guinea
does
seem
has
when
androgens
(Zimbelman
been
Accepted
Received
and
suggested
that
January
July
had
31,
Lauderdale,
the
concept
At
160
capable
of
(Elsaesser
of
pigs
days,
the
sow
at
stimulatory
in the female
MATERIALS
General
It
the
160
days
of
mechanism
is
Landrace
A
to evaluate
gilt
further
the effect
given
to
treatment
stages
and
to compare
in male
and
6 and
in
for
(Ford
1978).
estrogen
activity
was
surge
designed
propionate
different
pig
LU
Foxcroft,
was
testosterone
the
at both
the
operating
and
experiment
neo-
1973).
Landrace
age.
to exist
given
to
female
Uearn,
1978).
mechanism
been
developed
apply
pig
is sexually
dimorphic
in the miniature
pig at 14
days
of age (Elsaesser
et al., 1978)
and cyclic
activity
of sows
was not affected
during
adulthood
natally
not
rat
for
not
1973;
Hodges
and
estrogen
feedback
differentiation
does
Schanbacher,
1977).
The
purpose
of this study
the
LU response
to estradiol-17a
release
by
of fetal
Sherwood,
1971),
hamster
and
sheep
(Short,
1974;
1975),
whereas
in monkeys
of the stimulatory
estro-
and
(Buhl
et al., 1978)
Karsch
and Foster,
a sexual
dimorphism
(Brown-Grant
gen
hypothalamic
of
differentiation
of
pregnancy
feedback
and
on
the
ovarian
offspring.
AND
METHODS
Details
German
Landrace
pigs were kept under
lighting
conditions
and received
standard
pig
and water.
For hormonal
analyses,
2-5
ml
Domestic
of sexual
natural
chow
blood
either
from
samples
were
collected
at
1000
h or
2200
by jugular venipuncture
in 6-day-old
piglets
an ear vein in older animals
as described
Hultsch
(1979).
Jugular venipuncture
has no effect
8, 1979.
1978.
1187
h
or
by
on
ELSAESSER
1188
the
plasma
levels
Heparinized
plasma
always
administered
Hormonal
of
LH (Elsaesser
et al.,
was stored
at -20#{176}C.Steroids
i.m.
AND
1976).
were
Analysis
Plasma
LH was determined
as described
previously
by
Pomerantz
et a!. (1974).
Sensitive
and
specific
porcine
LH antiserum
(a gift from
Dr. G. D. Niswender)
was
diluted
to
120,000
and
100
p1 bound
‘\,40%
of LH in the absence
of unlabelled
LH. The LH
standard
preparation
(LER-786-3,
a gift from
Dr. L. E.
Reichert,
Jr.) was equal
to 0.65
NIH-LH-S1/mg.
Plasma
testosterone
was
measured
by
specific
radioimmunoassay
without
prior
chromatography
as
described
previously
by Ellendorff
et al. (1975).
The
antiserum
used
had been
raised
in a miniature
pig by
intradermal
immunization
against
testosterone
3carboxyoxime-bovine
serum
albumin.
This
antiserum
was diluted
1:20,000.
The antibody
cross reacted
23%
with
5-DHT,
2.8% with
5n-androsten-3,
17-diol,
less
than
1% with
estradiol-17a
and less than
0.1%
with
androst-4-ene-3
, I 7-dione,
progesterone
and
hydrocortisone.
Plasma
estradiol-17j3
was measured
by
radioimmunoassay
without
prior
chromatography
(Elsaesser
et
al.,
1978).
The
estradiol
antiserum
(provided
by
Drs.
Kuss
and
G#{246}bel, Munich)
was
directed
against
estradiol-1
713-6-carboxy-0-methyloxime-bovine
serum
albumin
and
cross
reacted
less
than
1% with
estrone,
estriol
and estradiol-benzoate
and
less than
0.1%
with
testosterone,
androst-4-ene3,17-dione
and
progesterone.
The
lower
limit
of
detection
for this assay
was 10 pg. The accuracy
and
precision
of each
assay
were
estimated
from
blank
values
(for
samples
of water)
and values
for plasma
samples
containing
high
and
low
concentrations
of
testosterone
and estradiol-17j3,
respectively.
The inter
and
intraassay
coefficients
of variation
were
14.4%
and
10.2%,
respectively,
for
the
determination
of
testosterone
and 13.3%
and 9.0%,
respectively,
for the
determination
of estradiol-171.
PARVIZI
pregnancy,
i.m.
(Schering,
Berlin;
injections
of
each
testosterone
propionate
injection
5 mg/kg
BW in a
concentration
of 50 mg/mI
sesame
oil) were given
on
3 occasions
separated
by 2 day intervals.
These
treatments
are referred
to as D 30, D 50, etc., for the
purpose
of convenience.
A further
group
of 4 sows
remained
untreated.
Blood
samples
for measurement
of plasma
testosterone
concentrations
were
taken
on
Day 2 and Day 3 after
the first injection.
At birth
(all animals
were born
within
2 months
of
each
other),
at 160 and at 250 days
of age the body
weight
as well as the effect
of the testosterone
propionate
injections
on the
size
and
appearance
of the
external
genitalia
of the female
offspring
was assessed.
At the
age of 160
days,
the response
of LH to
estradiol
was tested
in the female
offspring
(for n see
Fig.
3) as well
as in untreated
females (n = 8) and
males
(n = 7) that
had been
gonadectomized
at weaning (6 weeks
of age). All animals
were
treated
at 1000
h with
a single
i.m.
injection
of 60 pg/kg
BW of
estradiol
benzoate,
a dose
that
elicits
an LH surge
in
guts
of
this
age
(Elsaesser
and
Foxcroft,
1978).
Castrated
male
(n = 6) and intact
female
controls
(n =
8) received
sesame
oil. Blood
samples
for measurement
of plasma
LH concentrations
were
taken
at -12 h,
immediately
before
injection
and 24, 48, 60, 72 and
84 h later.
In males,
an additional
blood
sample
was
taken
at 96 h because
Ford
and Schanbacher
(1977)
suggested
positive
feedback
action
in the
castrated
boar
96 h after
treatment
with
estradiol
benzoate.
Concentrations
of estradiol-1
73 were
measured
at 24
and 72 h.
To check
on differences
in the degree
of sexual
maturation,
in addition
to daily
control
of estrous
behavior
starting
on Day
160 of age, all females
were
slaughtered
at 250 days of age. The reproductive
tract
was removed,
the uterus
and the ovaries were weighed
and
the
ovaries
were
inspected
for
occurrence
of
ovulation.
RESULTS
Statistical
Analysis
Student’s
Estrogen
test
(Snedecor,
1956)
was
detect
significant
differences
between
groups.
are expressed
as means
± SEM.
t
used
to
Results
Feedback
6-Day-Old
Female
and Female
A total
Effect
Functioning
Feedback
A
total
205 kg,
Starting
LU
of 35 male
piglets
was
gonadectomized
at
3
Testosterone
Treatment
on the
of the Estrogen
and the Ovaries
of 14 pregnant
sows,
mean
body
was
divided
into 5 groups
of 2 or
either
on
Day
30,
50,
70, 90 or
weight
3 sows.
106
of
concentrations
male
influenced
by
600
pg estradiol
Pigs
of Prenatal
plasma
gonadectomized
days
of age.
At 1000
h, 6 days
after
birth,
these
animals
and 31 intact
female
litter
mates
received
i.m.
injections
of 60 or 600 pg/kg
BW estradiol
benzoate
(0.5
mg and
5.0 mg/mI
oil, respectively;
Progynon
B
Oleosum,
Schering,
Berlin)
in a total
of 120-290
p1 of sesame
oil, or sesame
oil alone.
Blood
samples
were
collected
at -12 h, immediately
before
and 24,
48,
60,
72, 84,
96 and
120
h after
the
injection.
Pro pionate
and
Pigs
The
Estrogen
Feedback
in 6-Day-Old
Male
in
Male
pigs
treatment
with
benzoate/kg
in neonatal
1) were
not
(Fig.
either
60 pg or
BW. The concen-
trations
of estradiol-17j3
in
castrated
males
not
were low (‘20
pg/ml)
treated
with
estradiol
benzoate
receiving
to 26 ± 5 pg/mI
benzoate/kg
BW.
the
and increased
60 pg estradiol
injection
of
pg
estradiol
benzoate/kg
the
mean
estradiol-17a
concentrations
234 ± 36 pg at 24 h and at 96 h the value
pg/ml
plasma)
was
not
significantly
BW,
were
(20
different
from
animals.
The
plasma
neonatal
suppressed
of
600
after
After
600
that
at
in
concentrations
pig were
female
pg
observed
24 h only
estradiol
of
significantly
after
benzoate/kg
the
the
control
LU
in
the
(P’0.05)
administration
BW
and
then
SEXUAL
DIFFERENTIATION
OF
ESTROGEN
FEEI)BACK
distance
(11)
and
(10)
vulva
60
D
was
250
70
at birth
as well
of
Necrotic
tissue
in
at
in
of
the
3 of
birth,
appearance
normal
age.
observed
animals
The
1189
PIG
increased
days
was
IN THE
but
the
4 of 11
later.
was
genitalia
D 106
and
on
and
disappeared
external
the
D 90
4 D 50
as at 160
offspring.
female
#{176}
Estrogen
(11)
at
6
00
20
Feedback
160
Days
In
the
(Fig.
the
icantly
(12)
(10)
,
then
the
face
FIG.
1. Concentrations
of LH (open
bars)
and
estradiol-1713
(. logarithmic
scale!)
in the plasma
of
orchidectomized
male
and
intact
female
pigs
after
treatment
with
sesame
oil (OIL)
or estradiol
benzoate
(EB)
at 6 days
or age. V, plasma
concentration
of
estradiol-17p
20
pg/mI.
Results
are means
±
SEM;
number
of pigs are shown
in parentheses.
pig
again.
benzoate/kg
Treatment
with
was
BW
60
of
without
effect
on
Female
treated
2)
responded
later.
of LU.
The plasma
levels
after
the
injection
of estradiol-17f3
of either
60
estradiol
benzoate/kg
from
those
observed
BW
in the
were
600
the
In
pregnant
on
Day
testosterone
2
plasma
and
Day
propionate
12.6-18.9
high:
sow,
ng/ml
respectively.
The
stage
male
testosterone
propionate
levels
in
the
5
pg/ml)
of
apparent
testosterone.
Two
with
testosterone
50
of
animals
with
with
whose
testosterone
to
the
a
significant
with
oil
injection
of
injection
had
at the expected
was normal
been
treated
with
not
4
of
10
D 30
estradiol
(P0.05,
controls)
LU
of
48
in
h and
estradiol
the
60
h
benzoate
(6)
(8)
(7)
(8)
which
L
administered
had
levels
had been
starting
deliver.
time
rr}1
except
All other
in
of
treated
on Day
(112-116
sows
days).
one
sow
that
propionate
testosterone
females
were
(Fig.
first
very
ng/ml,
at
starting
on Day
106
and in which
was prolonged
and 5 piglets
died.
In
of
increase
treated
concentrations
The
mothers
propionate
testos-
were
endogenous
sows
that
propionate
did
pregnancy
farrowed
Parturition
on
effect
benzoate/
estradiol
C
no
6-day-old
following
pg
the
pregnancy
was
than
of
390
±
pigs.
of
3 after
injection
and 23.2-30.2
of
(1072
different
not
Prenatal
Testosterone
Pro pio nate Treatment
terone
pg
pigs
levels
h
±
such
male
plasma
24
No
females
in
or
neonatal
60
control
not
plasma
levels
26
h).
estra-
kg BW.
compared
estradiol
pg
at
in
of
administration
6-day-old
higher
1;
administration
benzoate
increased
much
(Fig.
72
The
2)
the
BW
levels
the
to
1).
(Fig.
after
levels
at
after
(Fig.
were
male
pg/mI
levels
h
pretreatment
plasma
benzoate
observed
pg/ml)
24
pig
signif-
were
benzoate/kg
to
37
LU
estradiol-17j3
(horns)
LII
estradiol
elevated
±
of
estradiol
was
I,me
still
(290
depression
pg
steadily
rose
of
male
of
suppressed
60
of
diol-1713
2269620
gonadectomized
concentrations
(P0.01)
and
of
Age
160-day-old
2)
injection
i-i-’iii1
‘#{176}#{176}
of
the
parturition
ano-genital
,,,,e
(boo’s)
FIG.
2. Concentrations
of LH (open
bars) and
estradiol-17i3
(s, logarithmic
scale!)
in the plasma
of
orchidectomized
male
and
intact
female
pigs
after
treatment
with
sesame
oil (OIL)
or estradiol
benzoate
(EB)
at 160 days
of age. V, plasma
concentration
of
estradiol-171
20
pg/mi.
Results
are means
±
SEM;
number
of pigs are shown
in parentheses.
1190
ELSAESSER
The
the plasma.
in
17j3
concentrations
AND
PARVIZI
at 24 h
and
72 h supraphysiological
were
725 ± 183 levels
and
314
± 64 pg
produced
of estradiolestradiol/mI
plasma,
respectively.
Figure
3
=
the LU
response
to estradiol
benzoate
treatment
at 160 days of age in gilts that had
been exposed
to testosterone
in fetal life. A
shows
small
increase
in D
30
compared
animals.
In
both
70 gilts
h or both
these
groups
as well
the response
to estradiol
was significantly
reduced
D
compared
with
Fig.
controls;
responded
estradiol
2). The D
to the
with
a surge
from
that
treated
oil treated
with
injection
of
not
LU
observed
control
.
at 48 or 60
(P0.05,
treated
106 gilts
of
benzoate
0
N
“20
N
OS
N
‘0
.
significantly
different
estradiol
benzoate
‘-
E#{176}
animals.
‘
.,SL)-
.
,
._.. Q
1
Q
VS
VSOOVSOVSO
exception
the
of
the
of
gilts
D
30
with
pretreated
,
us
body
females,
testosterone
50
was
control
(Table
not
significantly
groups
atlday,160
different
from
&
or 25Odays
of
and 250 of age
of estrous
behavior
was erratic
in all
not
related
to the weights
of the
1).
occurrence
groups
...
0
*‘n
VS.-N
propionate
both
=
C
With
age
N
VSOVS’2610
..
=
Ovary
weight
#{176}
N -
-
E
the
:
R
Functioning
of
:
..s
the
benzoate
90
and D
in
9
control
as in
estradiol
2
‘
in plasma LU levels was observed
D 50 females
but this was not
and
significant
<
and
Between
Days
160
V106S*VS
VS
,
a
070
“
(70
I
60
N
4N,ON
N.’VS*VSN...
,-0
(4)
0
0
-.--..-.22
‘
050
N
j
‘0
(10)
NONNNI...VS
01 OSVS’OVS
.
‘
.9u
0 30
:
55
S
>
,.
‘0
OOVSVSNVSVS
o
o
=H=44=44=
N
N
0
VS
N
N
1’
C
2
21
8.
g
‘0
U
.
00
N
0i
.,2o2a60,2,s
C
.,,rfl4$,o7?,
0
>‘
.0
U
#{149}
(9)
LIst
:i++J
.12
0
24
41
60
72
I
i.
‘s
tIc
U
0
0
.------..-
NO0N
a
9
VS
*‘-.
VS
VS
VS
ooooooo
F05
I
24
.12
0
24
48
60
2
C
S
00
VS
VS
84
a
VS
N
VS
U
testosterone
propionate
of pregnancy.
V, plasma
concentration
17)
20
pg/mi.
Results
are means
of pigs are shown
in parentheses.
±
of estradiolSEM;
number
V
a.
.0
.5
of
had been treated with
on Day 30, 50, 70, 90 or 106
0
-c
I
LH (open
bars)
and
scale!)
in the plasma of
treatment
with
estradiol
at 160
days
of age.
The
I
S
VS
.
(hours)
8
0
VS
‘0
U
FIG.
3. Concentrations
estradiol-17a
(.,
logarithmic
intact
female
pigs
after
benzoate
(60
pg/kg
BW)
mothers
of these
animals
00
>1
.0
t41+441101
0.
0
I,m.
C
C
‘0’ON’OVS’O’O
C
6
0
U
n
#{176}
C
21
====,=,
**‘OVSNO.-.
‘0
0
.
0 106 (7)
0
,
0
0 90
-8
‘0
E
a
0
*640..VVSNVS
C
-12024416072.4
.
i
‘6
I
“
“
I
.a
.
0
0
‘I
u
<
a.
I
‘0
.
00000
I
N
000
I
a.
:
.
1,
.
7-.
.
7-
a
a.
7-.
a.
1-
7-
J
0
‘I
a.
SEXUAL
ovaries
and
uteri
despite
the
slaughtered
cycle
(if
they
of
the
that
on
the
ovaries
of
groups
as the
animals
effect
or oil
of
weights
of the
not
70
of
ovaries
in
D
weight
Also,
the uteri
as well
corpora
of
the
not
uterus
but this
significant.
interesting
One
feature
that
finding
been
observed
in
of the
the
present
study
pig, as has
Landrace
previously
in
the
14-day-old
and castrated miniature
pig (Elsaesser et
1978),
the stimulatory
estrogen
feedback
intact
al.,
on
LH
release
is sexually
160 days
of age only
the
ponded
to
with
the
a clear
levels
explained
to estradiol.
castrate
only
occurred;
LH
although
still
negative
A
by
Ford
daily
similar
and
of
also,
following
a
in
exceed
the
i.m.
in
of
crystalline
rhesus
estradiol
to
be
mechanism
by
pig
At
that
be
of
negative
in
the
surges
s.c.
orchidectomized
subsequent
LU
the
of
in
al.,
whether
activated
the
in
the
LU
a sexual
feedback
estrogen
female
exists,
feedback
than
in
the
of
further
newborn
male
in
the
et
1974).
same
Uow-
in
these
al.,
LU
in
a surgelike
preovulatory
been
surge,
studied
possibility
so
stimulatory
estrogen
to
and
mechanism
and
of
pregnant
the
ovary
given
days
p.c.
by
it is tempting
period
might
these
in
of
to
sexual
the
utero
affect
in
stimulatory
did
not
feedback
striking-
function
although
implants)
to
of
Recently,
reproductive
offspring,
testosterone
by
stimulatory
administration
testosterone
on
explained
reported
Androgenization
by exposure
terone
the
animals.
1977)
of
ewes
female
(Silastic
be
of
(1976a,b,
is maturing
the
40-60
and
functioning
effects
different.
monkeys
be affectwhen
critical
feedback
in
could
of the
control
of LU release
the pig at this time.
The impaired
impaired
similar
is
feed-
of fetal
life.
In this
that
elevated
serum
have been observed
between
the
in
al.
study
ovary
et al. (1978)
that
et
is
of this
stimulatory
treatment,
pig fetuses
functioning
the
the
Days
30 and 70
it is of interest
concentrations
differentiation
takes
place
of
finding
of the
testosterone
between
context
testosterone
the
mechanism
(Caligaris
et al., 1972;
An1977)
before
22 days
of age.
important
functioning
by
the
species
feedback
operate
Ojeda,
Another
the
the
in
a
far
steroid
is that
hypothalamus
in which
male.
With
pulse
studies
pituitary
not
steroid
receptors
the
newborn
rat,
ly
the
suggesting
A
in a short
previous
the
a
Karsch,
of the
of
of
nique
dimorphism
the
to
estrogen
observed
in
LHRU
of
has
the
has
or pituitary
and Plapinger
an immaturity
It
surge
LU
our
that
the
to release
to
the
point
Foster
and
the pituitary
pituitary
which
to
which
receptors
in the
hypothalamus
are lacking.
Kato
et al. (1971)
and McEwen
(1973)
have shown
Clarke
castrated
stimulatory
to that
because
similar
of
1973).
the
a possibility
in the pig.
estrogen
adult
injections
et
manner
speculate
containing
findings
the
1970;
that
ever,
it is possible
animals
is not able
in male
treatment.
age
estrogen
the
the
that
in
mechanism
to release
out,
Colenbrander
not
plasma
observed
(Karsch
a similar
6 days
negative
earlier
then
determined
can
by
capsules
in
did
If
1971).
those
with
estradiol
and
suppressed
silastic
benzoate
remains
of
levels
al.,
et
can be induced
monkeys
by
female
male
control
resembling
is unable
Foxcroft,
work
pig
similar
et al.,
possibility
of
than
and
or female
pig responds
to
way as the adult
(Elsaesser
ed
concentrations
LU
estradiol-17(3,
secretion
boars
pig
the
doses
our
These
of
be ruled
back
follow-
all.
we
160-day-old
feedback
at
(Land
The
showed
that
been
it should
be
male
rhesus
injection
are
concentrations
(1977)
castrated
single
implantation
has
expands
maturation
sheep
1975).
unable
drews
levels,
713 were
castrated
depressed
returned
to
them
(Yamaji
benzoate
male
feedback
this context
the
in
160-day-old
observation
In
that,
monkey
differences
Schanbacher
benzoate.
mentioned
differ
cannot
estrogen
treatment
estradiol
not
rose to pretreatment
levels
of estradiol-1
plasma
elevated.
made
of
and
levels
did
In the
levels
the
treatment
dimorphism
basis
the
at
res-
benzoate
our
estradiol
sexual
on
sensitivity
LU
estradiol
Because
treatment
the
sexes,
ing
LU.
following
between
be
of
supraphysiological
produced
the
of
injection
surge
differentiated:
female
animal
(Elsaesser
estrogen
newborn
the
gilts
feedback,
pronounced
various
in
Landrace
developed
could
to
study
female
1191
estrogen
a more
that
occurred
this
and
PIG
response
60-day-old
gradual
feedback
DISCUSSION
is
IN THE
stimulatory
shown
stimulatory
(Table
animals,
in
newborn
lutea
declined
to the
recently
1978)
controls).
and
50
was
with
with
had
FEEDBACK
LU
release
in
estradiol
benzoate
estrous
the
compared
treated
animals
depressed
was
D
weights
the
albicantia
also
and
(P0.01
corpora
1). The
were
regard
have
30
percentage
and/or
days of age. Uowever,
the
animals
were
not
D
benzoate
in these
ESTROGEN
the
reduced
estradiol
OF
same
day of
started
to cycle),
had
significantly
250
at
fact
DIFFERENTIATION
their
techwas very
of female
exogenous
the
rhesus
testos-
functioning
mechanism
(Stein-
ELSAESSER
1192
er et
al.,
1976).
This
is in agreement
with
findings,
which
indicate
that the control
governing
cyclic
gonadotropin
secretion
not
to be differentiated
in this species
et
AND
other
1977)
system
seems
(Karsch
The
pig
fetus
the
administered
linization
seems
althouth
plasma
peripheral
propionate
we
treated
as high
treated
well
of
pig and the
to estradiol
protected
mascusuppres-
than
mothers
were
untreated
as in the
1 sow
levels
testosterone
testosterone
of
the
with
i.m.
at
in
least
mothers.
and
an empty
50
of
160
days
age.
of
factors:
This
in
the
of
brain
permeability
late
be due
testosterone
is supported
uterus
that
occurs
to
C19
testosterone
antagonist
effect
in the
and
during
the
of
including
we
by
an
concentrations
1973;
to
1975).
There
can act as a
protect
in the
of
late
gestation
Baldwin
and
during
against
of
testosterone
rat (Diamond
et
adulthood
to
to estrone
know
that
Stabenfeldt,
1975;
Ash and Ueap,
is also evidence
that
progesterone
masculinizing
neonatal
life
testosterone,
steroids,
plasma
estrone
Wagner,
tissue
decrease
The last possibility
of Fevre
(1970)
be converted
Moreover,
in
and
and
target
the
testosterone
aromatization
in the placenta.
by the findings
showed
increase
the
life,
transfer
of
of increased
testosterone,
can
the
pig placenta.
estradiol
(Molokwu
fetal
90
the
at
to a number
of the
in
of
the diminished
fetus
as a result
who
might
guinea
the
during
al., 1973)
pig
mond
and Young,
1963).
This
protective
of progesterone
could
also be functioning
(Diaeffect
in the
pig
fetus
in which
the
plasma
progesterone
levels
are very high late in pregnancy
(Elsaesser
et al., 1976;
Macdonald
et al., 1979).
We
conclude
of
prenatal
on
to
the
the
the
1971)
that
or
neonatal
with
respect
testosterone
to
the
effect
treatment
LH surge
mechanism,
the pig is similar
rat (Barraclough,
1966;
Gorski,
1973),
guinea
and
pig
the
(Brown-Grant
sheep
(Clarke
rhesus
monkey
is
in the LU
possible
a qualitative
of the
male
response
that
the
response
rather
difference.
ACKNOWLEDGMENTS
This
work
was supported
by the
Deutsche
Forschungsgemeinschaft.
We would
like to thank
Schering
AG/Berlin
for the generous
gift of testosterone
propionate.
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