BIOLOGY
OF
REPRODUCTION
19,
Prolonged
Progesterone
CHRISTIAN
The
807-816
(1978)
Gestation,
Elevated Preparturitional
Plasma
and Reproductive
Aging in C57BL/6J
Mice’
F. HOLINKA2,
Andrus
YUEH-CHU
Gerontology
and
Center
University
Los
TSENG
the
CALEB
E. FINCH
of Molecular
Department
Biology
California
of Southern
California
Angeles,
and
90007
ABSTRACT
Gestation
months
is prolonged
to
20.8
days
decreased
sharply
11-12-month-old
turitional
at
during
aging
in previously
11-12
months.
after Day 16 of gestation
mice was 55% less than
progesterone
levels were
parous
Plasma
in
3-7
in the
month-old-mice,
younger
from
by
whereas
group.
correlated
inversely
C57BL/6J
mice
measured
progesterone,
18.6 days at 3-7
radioimmunoassay,
the
rate
In 3-7-month-old
with the number
(P<0.05)
of
decrease
in
mice,
prepar-
of viable
fetuses
on Day 18, whereas
such a correlation
(P<0.05)
persisted
from Days 19-22
in the older
mice.
In
11-12-month-old
mice, gestation length was inversely
correlated
with
litter
size; no significant
correlation
was found
in the younger
group at first or second
pregnancy.
Because
the decline of progesterone
is generally
considered
necessary
for parturition
in rodents,
the retarded
decrease
of progesterone
in 11-12-month-old
mice is likely to be a major factor in their prolonged
gestation.
In
3-7-month-old
mice at first pregnancy,
the gestation length was significantly
longer
(19.0
days)
and the litter size smaller (6.5 pups) than at second pregnancy.
Average
litter size decreased with
age in previously
parous
mice
from
7.8
pups in 3-7-month-old
mothers
to 4.6 pups
in 11-12month-old
mothers.
Mortality at birth
increased
with gestation
length in 11-12-month-old
mice.
The influence
of litter size on the luteotropic
and luteolytic
mechanisms
during
the period
preceed-
ing parturition
is discussed,
INTRODUCTION
Among
declining
factors
fertility
irreversible
increasing
decrease
irregularities
(reviewed
in
Increased
of
Finch,
gestation
increased
with
fetal
failure
required
to
hamsters,
reported
et
mortality.
some
age
could
al.,
al.,
and
with
with
prolonged
to
late
have
in
relatively
gestation
Leavitt,
The
maintenance
and
high
plasma
(Blaha
and
in the
Michael
1970;
Morishige
child,
1972,
Received
‘Contribution
Laboratory.
2Dept.
School
of
of
24,
of Obstetrics
Medicine,
and
New
Gynecology,
York,
New
1970),
agent;
Neurobiology
Mt.
York
before
al.,
et
starting
around
declines
parturition
Greenwald,
1974;
1975)
al.,
1974).
in mice
Murr
and
1973;
The
drop
Moore,
rats
Pepe
et al.,
(Wiest,
and
importance
of progesterone
1963;
Madhwa
Additionally,
the
decrease
(Loewit,
LH
the
rise,
progesterone
2 days
et
Morishige
et
1972,
1974),
rapidly
during
early
a plateau
which
is
second
et
and
Rothof
the
is suggest-
ed by the prolongation
of gestation
by injection
of progesterone
in mice
(Kroc
et al.,
1959;
Porter,
1975)
or rats
(Walker
and
Matthews,
gesterone
1978
16, 1978
No.
33
from
a
preparturitional
1970).
April
January
1974;Michael
rises
reaches
and
1974;
1949;
Accepted
McCormack
et al.,
Finally,
(McCormack
gesta-
termination
by
regulated
and estradiol
In young
mice
1957;
Murr
progesterone
and
midpregnancy.
a
on
and rats (Wiest,
1970;
Pepe
and
Rothchild,
followed
physiologic
mechanisms
in rodents.
In aging
animals
1975)
1973;
rapidly
from
depends
Hooker,
1974;
plasma
pregnancy
gestation
result
and
Greenwald,
aging
al.,
1959)
is associated
tion
appeared
progesterone
1974).
onset,
in
pregnancy
of plasma
progesterone
et al., 1973;Ryan,
1973).
(Forbes
is an addiprolonged
Prolonged
maternal
the
and
cycle
1977).
et aL, 1960),
experimentally
activate
the
for
parturition
are
Talbert,
(Kroc
1963)
changes
(Heap
with
ovarian
oocytes
of the ovulatory
length,
mice
1961,
advanced
associated
rodents
1977;
hamsters
(Soderwall
tional
variable,
since
gestation
in
rats
(Moore,
mammalian
commonly
in aging
was
1970;
which
delayed
delayed
Madhwa
presumably
parturition
Raj
and
Moudgal,
pro-
preparturitional
by
Raj
injections
and
of
Moudgal,
acted
as a luteotropic
also
resulted
from
this treatment.
Sinai
10029
In the
807
following
study
of reproductive
aging
808
HOLINKA
in C57BL/6J
gestation
was
of age-related
ity
and
the
mice,
extensive
prolongation
observed
and
changes
in litter
regulation
of
is analyzed
size,
of
in
fetal
plasma
terms
mortal-
progesterone
levels.
MATERIALS
Eight
C3HeB/FeJ
retired
atory;
housed
AND
METHODS
to
10-week-old
males
and
virgin
C57BL/6J
8-monthold
bought
from
females
C57BL/6J
the Jackson
and
female
for
variable
time
periods
before
mating.
The
cages were
changed
twice
a week.
Two
females
were
mated with 1 male and checked
for vaginal plugs daily
before
1200
h. When
plugs
were found,
mice were
housed
singly
and
given a breeding
pouch
for nest
building.
Males
were
considered
proven
if
breeders
they had fertilized
at least
1 young
female
that subsequently
gave birth
to a healthy
litter. The males were
used
as breeders
continuously
between
the age of 3
and
9
old,
mum
which
in C57BL/6J
fertility;
the
aged
months.
retired
The
young
females
were
3-7-months-
mice
is the period
of
females,
11-12-month-old
maxi-
breeders,
were at an age of reproductive
decline
Hormonal
levels in young
females
were determined
during second pregnancy
because
the
reproductive
performance
of primiparous
mice (based
on litter
size) is suboptimum
by comparison
with
multiparous,
young adult mice (Biggers
et aI., 1962;
(Talbert,
1971).
1).
These
studies
June
and
1976
(
mice
were
1977.
a related
season
does
between
litter
size
not seem
November
in C57BL
to be influenced
and
Payne,
1970),
efforts
matings
and samplings
distribute
uniformly
throughout
the
were
during
experimental
Number
43%
of Pups
gave
of
the
older
significant
mothers,
delivered
overnight
at P < 0.05;
birth
during
the day.
For example,
a mother
found
with
pups
in the
morning
of Day
20 (Day
1 = day of vaginal
plug) had a 19 day gestation
period,
whereas
one giving
birth
on Day 20 in the afternoon
had a 19.5
Blood
Elimination
with
Pathologic
Gross
Because
with
day period.
Collection
Blood
samples
2230.
Approximately
and
Laporatomy
were
1
,2-propanediol.
collected
between
1800 and
5 mm after anesthesia
by i.p.
of Mice
Lesions
pathologic
lesions
deficiencies,
gross
reproductive
may
such
be associated
as impaired
testicular
function
in 29-31-month-old
mice
(Nelson
et al,, 1975),
all females
cally
examined
after
exsanguination.
senescent
males
(Nelson
et al., 1975),
present
11-12-month-old
male C57BL/6J
were
systematiIn contrast
to
lesions
in the
were rare. (AddHolinka
et al.,
in
females
itional
details
will
be reported,
preparation.)
Six of 188,
11-12-month-old
were
eliminated;
4
showed
severe
and
2
showed
general
weakness,
females
splenomegaly
accompanied
by
an
unhealthy,
edematous
appearance
of the viscera.
Of
these
2, the adrenals
were bilaterally
enlarged
in 1 and
in the other,
they
were
abnormally
pink-red
in color.
In general,
female
C57BL/6J
mice are vigorous
and
healthy
at 11-12
months,
an age less than
half of the
mean lifespan
et al., 1976).
(Kunstyr
by
plasma
RIA
with
hexane:ethyl
extracts
were
and
cpm
2200
of
serum
of
to
albumin
Endocrine
a
con-
Sciences,
acetate
100:1.
=
incubated
(3H-1,2]
with
After
antiserum
progesterone
(56
72.5%
(NH4 )2SO4.
Standard
curves
alone
or added
to plasma
from
mice, calculated as % free/%
bound
vs
were
of
samples
ant’thodies
England
Nuclear,
Boston,
MA).
Free
was assayed
by liquid
scintillation
precipitation
of
antibody-bound
progesterone
with
with
progesterone
ovariectomized
progesterone,
Leto
to the protocol
of Endocrine
was extracted
from 5-20
zl of
Progesterone
Ci/mmole,
New
j3 H] -progesterone
counting
after
in
rabbit
P11-192,
evaporation,
recovery
measured
1-succinate-bovine
with
1975;
(RIA)
was
(Antiserum
No.
CA) according
Sciences.
Leuenberger,
Radioimmunoassay
mice
jugate
Tarzana,
and
progesterone
progesterone-i
X2
3.85; df = 1).
Mature
mice generally give birth
in the early
morning
hours
(Rafferty,
1970).
Diurnal
births
usually
occurred
in the late afternoon
under
conditions
of a 12 h
light
cycle,
turned
on at 0800
h. One
half day was
added
in calculating
the gestation
length
of animals
that
Necropsy:
individual
It was
assumed
that
fertilization
occurred
in the
early
morning
of the day of the vaginal
plug (Rafferty,
1970).
During
late pregnancy,
mothers
were
checked
for births
twice
a day, between
0800-1000
h and
1800-2000
h. The majority
(76%)
of the
young,
but
(difference
in
3-7-month-old,
had given
birth
on Day
19, see Table
2), the
number
of newborn
pups
and
the gestation
period
were
determined,
as described
above,
while
the remaining
pregnant
mice
were
laparotomized
for
fetal inspection.
Plasma
of Gestation
and
stock
After bleeding,
mice were Iaparotomized
to determine the number
of total and viable fetuses and then
killed for necropsy
(see below).
On those days when
some mice had already
given birth
(i.e.,
10/20
mice,
Progesterone
Determination
Length
undertaken
Although
strain)
(Franks
made
to
gestation
period.
only
of 0.30-0.45
ml
of 2,2 ,2-tribromoethanol
(Matheson,
Coleman
and Bell, Norwood,
OH)
(Holinka and Finch,
1977),
blood
(0.4-1.1
ml) was obtained
by retroorbital
puncture.
A 3.7% tribromoethanol
solution in 0.14
M saline
was prepared
fresh from a 50%
with
heparinized
Pasteur
pipets,
transferred
to heparinized
polystyrene
tubes, stored
on ice during
the experiment
and centrifuged
at 4#{176}C.
Plasma
was stored
at -70#{176}
C.
breeders
were
LaborBar Harbor, ME. The animals were quarantined,
and fed as previously
reported
(Holinka
and
1977).
With
few
exceptions,
they were kept
Finch,
5/cage
by
injection
w/v 2,2,2-tribromoethanol
Blood was collected
Mice
Table
ET AL.
linear
progesterone
from
5-150
carried
through
pg.
the
Final
entire
procedure
was 71.1 ± 1.65%.
The
plasma
values
were
thus
corrected
for the
recovery.
Coefficients
of
variation
were 18% (interassay)
and 7.2% (intraassay).
Statistical
Tests
Statistical
determined
significance
on
the
HP-97
(unless
otherwise
calculator
noted)
was
(Hewlett-Packard,
PROGESTERONE
AND
PROLONGED
GESTATION
Corvallis,
#{149}1’
-
‘
-
-‘
,,
N
fl
0’
0’
Pac
dard
1”
also
calculated
IN AGED
OR)
by
the
by
the
linear
Pearson
for
data
or
Pac,”
The
MICE
809
test
2 tailed
t
regression
correlation
in Table
program
in “Stat
program
in
coefficient
“Stanwas
3.
0’
0’
RESULTS
N
Gestation
length
was
influenced
by
reproductive
history
and
age.
In
3-7-month-old
mice,
gestation
at
second
pregnancy
was
shortened
Fig.
1).
I
IN
I
0
history,
I
IN
tween
“
‘ON
0’
N
comparisons
age
groups
mice
The
at second
no
gestation
N
0
I
,d’
I
N
confounding
reproductive
hormonal
based
on
(Table
of gestation
19.0
levels
mice
be-
of estab-
inthan11-12-month-old
in 3-7-month-
1, Fig.
periods
11-12-month-old
with
younger
>
-
00
0
group
gestation
of 232
C
,,
20.5
I-’
-
1,
of
1).
(Fig.
mothers
18.5
days
days;
and
only
in contrast,
1)
with
2 of
>90%
37
of the
‘I’s
‘0
I
18.6
days
(Table
determination
pregnancy
less than
(5.4%)
,U
-
lo
of
were
distribution
shows
I
Io
for
lished
fertility.
Gestation
mice
was
2.2 days
longer
‘N
old
,
to
N
I
Z ,n
0.4 days
Methods
gestation
length.)
To minimize
the
of
variables
associated
with
‘-I
by
(See
(first
or
days,
whereas
litter)
second
of 19 days or less.
(0.5%)
younger
mice
>75%
had
a
Conversely,
only 1
had a gestation
of
of
11-12-month-old
N
-‘
V
mothers
at that
birth
time
or later.
the
overlap
in gestation
periods
groups
is minimal.
Additionally,
that more
11-12-month-old
than
U
‘0
gave
Thus,
between
age
is of interest
it
younger
mice
U
gave
and
u
4)
V
The
‘
I’
0’
-
ZE
birth
-,0
N
._
during
daylight
hours
(see
Materials
plus
stillborn
Methods).
mean
o
increased
v
old
litter
at
size
second
(live
pregnancy
in
pups)
3-7-month-
N
0’
0.
0.
mice
to
11-12-month-old
7.8
Fig.
number
2).
The
pups
and
declined
mice
to 4.6 pups
of stillborn
by
40%
(Table
pups
in
1,
increased
0
‘4-
o
with
age
(Table
Since
1).
11-12-month-old
C
.9
0
00
U
VV
se
C
>‘
C
0.
U
‘0
V
V
.
..
70
60
C
‘0
-
o
VU
00
,
0
=
X
% mothers
80
0.
0.0
‘4
‘
.
0.
u.
0
4
40
EEE
22#{176}
‘0
50
30
20
mo
list
litter)
3-7
mo
(2nd
litter)
1H12
-
0
0.
3-7
V
O
.9
>
17
‘0
V
.
#{149}
‘#{176}
o
.e
C
0
U
#{176}
E 2
t..
U
aged
‘
FIG.
3-7
second
‘4
0’
9
GestatIon
20
21
length
22
23
24
(days)
C
N
00
I-’
8
‘0
C
‘4
U
‘
retired
1.
Distribution
months
pregnancy
breeders
at
of gestation
first
(n=19)
(n=37).
length
pregnancy
(n=214)
and
in
11-12
For mean
gestation
0
and
statistical
treatment,
see
Table
1.
in mice
and
months
lengths
810
HOLINKA
e----.
3-7
me
(let
3-7
me
(2nd
11-12
-‘
llttsr)
ET AL
df=
lItter)
me(multlpl.
litters)
1).
By
incidence
length
according
29.44L
to the
(days);
+
pups
had
6-10
FIG.
pups)
1,
2. Distribution
in mice
legend).
tion,
subgroup
size
litter
as a function
For
mean
Table
see
of
and
and age
size
of parity
litter
size
as
gestation
stillborn
(live
a function
SEM),
month-old
1.
1)
that
frequently
of stillbirths
age
cannibalized
their
pups,
is a minimal
estimate
group.
stillbirths
at
Whether
second
Gestation
length
11-12-month-old
the
following
the
be
was
of litter
total
P, was
coefficient
of
live
20.63
=
number
is
Table
occurred,
pregnant
mean
pups
only
0.24N;
-
gestation
of
that
on Day
19, none
birth
on that
day
postpartum
on
ers
on
born
that
given
born
and
(Fig.
had
and
Day
21,
3-7(Table
in analyzto
(measured
from
in both
of gestation.
age
Thereafter,
dropped
(average
Days
the
mice
steeply
decline
16-19),
in
of 23.7
where-
11-12-month-old
mice
(average
decline
of
Days
16-22;
Fig. 4).
fetuses
mice
N
3).
Day
20.
The
birth
decreases
compared
Day
decreased
22. The
likewise
21
not
and
32%
birth
in mean
moth-
with
those
20.
born
significant,
of mothers
The
means
19-22
correlation
or
of
plus
the
total
(Table
3). There
percent
not
the
number
of
with
number
of
correlated
in the
18, whereas
11-12such
correlations
of
resorptions)
(analysis
was
no signifi-
of viable
sites
(viable
plasma
fetuses
fetuses
progesterone
shown).
(P < 0.05;
significantly
X2
=
DISCUSSION
The
fetal
without
focus
gestation
development,
disturbance
litter
on
period
report
slowed
fetal
in implantation
size.
the
length,
litter
and
evaluate
changes
3.86;
prolonged
associ-
ated
with
elevated
plasma
progesterone
levels
reported
here for aging
mice
may have several,
possibly
interrelated
causes,
such
as delayed
implantation
with
consequent
retardation
in
smaller
of
significantly
fraction
of still-
increased
22
Days
cant
inversely
on Day
showed
differ
20. Whereas
had given
11-12-month-old
on
on
were
only
mothers
mice.
and
the
3-7-month-old
19 did
is not
statistically
to the small
number
live
pups
21 to Day
pups
of
Day
on Day
mothers
from
Day
20,
due
between
days
of the older
mice
had given
and only
4% (3 of 81) were
Day
pups
on
Day
probably
pups
on
significantly
from
of the 3-7-month-old
total
from
in
at parturition
live
postpartum
of
of
size
correlations
of average
plasma
progesterone
day of gestation
are given in the legend
of
Fig. 4. Older
mice still pregnant
on Days 20 and
21
showed
progesterone
levels
comparable
to
viable
younger
P < 0.001
length
of pups
number
number
that
±
is useful
levels
a
(mean
of
litter
size
11-12-month-old
those
on Day 18 in mature
Plasma
progesterone
2 lists,
for each
day on which
births
the number
of mice
that
were
still
vs those
that
had
given
birth.
The
mothers
and
The
month-old
is the
days
1 day
levels
mice
between
This
pups)
comparable
progesterone
3-7-month-old
ng/ml/day,
± SEM).
litter
of
as
average
levels
in
declined
more
slowly
10.8
ng/ml/day,
between
pups (live plus stillborn)
21.85
- 0.23N;
P < 0.001
=
L
subgroup
15-16
-585
with
L
where
This
Days
(10/3 7)
litters,
± 0.1
Discussion).
Plasma
progesterone
on
a subgroup
with
large
(5/69
by
whose
size
regression):
L
exceeds
mice,
were
at
with
mice
=
mean
20.0
average
to
significance,
of
mice)
dead
% stillborn
stillbirths
contributions
gestation
individual
were
1.
± 0.13,
the
age
according
correlation
(see
groups
from
in this
only,
(the
the
in
3-7-month-
a function
mice
from
in
ascertained
of stillbirths
equations
determined
is a decline
pregnancy
old
mice
can
not
generally
low incidence
group
(Table
1).
in
there
the
in
pups
to define
mice
7.2%
is similar.
ing
the
lengthened
mothers
number
equation:
P < 0.0
(6.9
which
(see Fig.
all
of stillbirths
increased
in
11-12-month-old
length
of
gesta-
22.5,
It is of interest
11-12-month-old
of
Litter
Day
birth.
The
gestation
observed
concerning
The
present
analysis
interrelationship
size
the
and
fetal
during
hormonal
maturation
and/or
of
progesterone
contribution
late
will
gestation
to
levels
the
pregnancy.
support
and
A
fetal
PROGESTERONE
AND
PROLONGED
00
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IN AGED
MICE
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3. Regression
FIG.
plus
L
=
21.85
N
=
no.
in
0.23N
-
(L
pups),
Day
length on litter size
11-12-month-old
gestation
=
length
in
days;
P<.001.
during
capacity
(4
lB
16
3
pregnancy
period
the
and
of
in
reproducdecline
day
16-22
and
25
Day
22
3
B
(P<0.001).
were
19
gestation.
significant
significant
vs
Day
Day
on
Differences
for younger
18 vs Day
(P<0.001)
18
and
19 vs Day
18 (P<O.05),
Stuof mean
plasma
progesterone
were:
N
collected
were
16 (P<O.05),
pregnancy
ng/ml;
Day of gestation
No. mice,
3-7 me
e
,ll-l2mo
during
19
(P<O.01),
P = 251.1-10.7N
was
21
groups
days
of
(P,
Blood
4
on Day
Regressions
test.
t
2
17 vs Day
and Day
mice
the
20
(0
age
successive
older
(9
progesterone
(P<0.005)
459.7-23.6N
month-old,
C57BL/6J
maximum
at reproductive
Plasma
between
between
for
throughout
tive
18
3
mice on Day
17 (P<0.005)
mothers:
dent’s
mice
13
4.
18
on
survival
17
Il
Differences
10
size
of gestation
stillborn)
of
16
FIG.
Litter
(live
5
15
-
C
is
the
once
3-7-month-old,
Days
P
16-19;
(P<O.001).
nth
day
of
only, under
=
11-12-
Days
pregnancy).
anesthesia.
is in
preparation.
Gestation
Because
Length
the
represent
Gestation
length
significantly,
between
pregnancy
in
1). In both
for
the
mice
was
young
mice
period
of
the
older
also
1;
had
given
days,
mice
had
increased
change
was
in
values
1963;
done
after
so.
23
aged
less than
10%
one
of
11-12-
a
Litter
by
Soderwall
et a!.,
although
here
for
the
corres-
1960).
variables
a
study
their
an
inverse
correlation
and
gestation
length
of
TO
reproductive
mice
lives”
between
(Biggers
mated
indicated
litter
et
a!.,
size
1963).
that
in
from
stages
of
were
However,
mice,
there
correlation
litter
correlation
size
TO
1962;
mice
the
decreased
litter
by
and
also
present
too
trend.
size
40%
x
mice
A)
shown
study
at
(sum
(Table
low
In
by
the
(Table
second
(Rugh
and
of stillbirths
was
a
mice,
pregnancy
(CBA
decreased
in CFI
mice
the
incidence
such
aging
at second
was
the
in
stillbirths
establish
the
1961),
CFI
mice
(Rugh
and
and TO mice (Biggers
et al.,
1963)
mice
length
that
length
and litter
al., 1963)
reflects
from
RI!!
first or
gestation
size
A,
Krohn,
1967)
Finn,
C57BL/6J
mice,
in litter
during
possible
of gestation
(Biggers
et
in CBA,
C57BL/6J
in
in 11-12-monthwas
a significant
thus
contribution
An increase
(Jones
and
Wohlfromm,
mice
is
It
mice
the
observed
as
aging,
separately
between
size.
inverse
in
as well
reproductive
considered
C57BL/6J
primarily
apparently
mice
study.
There
was
no significant
of gestation
length
on litter size in
3-7-month-old
inverse
study
virgin
second
pregnancy.
old
C57BL/6J
nancy
1967),
“throughout
various
Although
Size
Previously,
these
length
ponding
ages (Soderwall
et a!., 1960).
A relatively
small
increase
in gestation
length
with
maternal
age also
occurs
in
other
mammals
(reviewed
at
and
after
Gestation
hamsters,
the
a gestation
In
reported
of
of
occurred
days.
in
average
90%
mice
the
present
regression
Rugh,
prolonged
less than
birth
of
reported
an
birth
second
(Table
Over
whereas
mouse,
period
and
al.,
by
1).
but
mice
markedly
Fig.
19.5
month-old
gestation
et
mice,
(Table
first
it fell within
Gestation
days
the
(Biggers
11-12-month-old
2
slightly,
3-7-month-old
groups,
adult
1968).
decreased
data
offspring
1).
preg-
Wohlfromm,
in younger
(Table
1)
to
11-12-month-old
of live and
1).
The
stillborn)
decline
in
PROGESTERONE
.0
AND
en en
PROLONGED
C
U
to
,i.
strains
in
in
(Jones
1962;
in
ZZZZvvvv
and
previous
parity
the increase
ZZZZ
0
0’
0
.0
N
*
-
C57BL/6J
en
0’.
C
0
C
0
2
N
00
in
0000
in
V
‘0
II
V
factor
in
of
implantation
is
NN*N
‘4
N
*
only
N
II
Ii
younger
N
II
The
.0
et
0
2
a!.,
N
‘0
N
en
-
-
-
-
in
N
U
C
U
00
00
#{149}e
0000
ZZZvZ
‘4
tion
and
Z
0
0
N
0’
.0
0
C
0
V
2
.0
2
0
C
V
N
C
#{149}
0
‘
V
V
C
0
z
V
whether
mice
cause
for
there
are
(in
vasoconstricthe
smaller
in this study
their
prolonged
many
reports
length
with
smaller
litters
(reviewed
in Biggers
et
1963;
Holm,
1967),
relative increase
here
subgroup
in
.0
age
average
litter
size,
nonetheless
was
mice.
We
suggest
litter size
there
involved
11-12-month-old
‘
Z
0.
mothers.
of
than
Additionally,
a
C57BL/6J
mice
pups;
6.9
stillbirths
had an average
gestation
>1
day
longer
than
is
quency,
2
‘4-
older
to be smaller
by large
litters
(6
± SEM)
and
reduced
mean
0
-
a!.,
tends
of 11-12-month-old
smaller
.
0
44
progesterone
gestation
younger
V
‘4
(LoeMoore
increased
able
births
C
0
2‘4
that elevated
sufficient
LH
of
the
± .13,
(see
20.0
18.6
days,
day
average
gestation
of 3-7-month-old
mice
(2nd
pregnancy).
Although
the
11-12-month-old
subgroup
and the younger
mice
had a compar-
.
N
V
.0
0.
or
survival.
Although
Results)
which
0’
‘4
en
1963)
fetal
in
(Kroc
gestation.
defined
Z
‘0
0
1961,
of estradiol) causes
fetocidal ischemia.
hence
a
of
gestation
progesterone
of
reduced
suggests
observed
V
4-
Moore,
presence
the
V
of
U.’
4-
.0
prolongation
injections
by
the
are
V
‘4
that
et
The
question
arises
litters of 11-12-month-old
0
0
V
than
al., in preparation).
stillbirths in older mothers
of
1970)
(1963)
-
N
.0
early pregnancy
in
(15%
strikingly in positive correlation with
length (Table 2). It is relevant that
1959;
witt,
-
sites
(Holinka
number
experimental
young
rats
V
en
10 of gestation
is the
litter
size,
since
the
lower
mice)
increased
gestation
0
of
that
in 11-12-month-old
Day
reduced
slightly
It appears
,-.4i
.0.0.0.0.
Z
1963).
after
major
a!.,
Adsell et al., 1941;
of resorptions
number
et
and in hamsters
(Soderwall
mice, it is independent
(Finn,
mice
Biggers
and Wohlfromm,
Rugh
1916;
1958)
In TO
in other mouse
1961;
1963;
in rats (King,
Ingram
et a!.,
et a!., 1960).
‘0
Krohn,
Finn, 1962,
1967),
.0000
I)
813
MICE
litter size with age also occurred
vvvv
‘4
IN AGED
N
0000
V
U
GESTATION
or
the incidence
greater
than
that
in
of stillin the
addition
to
higher
resorption
freare
factors
specific
to maternal
in
the
prolonged
gestation
of
C57BL/6J
mice.
V
C
0
C
0
‘
.
Progesterone
0
U,
Plasma
progesterone
levels were
in both
age groups
at the peak
>‘
U
C
(4
2
V
0.
0
#{176}‘ .
‘4
0
15-16,
secretion
4-
in’0
-
-
N
000’
-
-
0
-
N
N
N
N
Fig. 4). This implies
by
the
corpus
luteum
comparable
days (Days
that progesterone
is
normal
and
that
luteotropic
support
produced
by
the
fetoplacental
unit is adequate,
irrespective of
814
HOLINKA
resorption
size,
levels
sites.
The
resorption
throughout
in a future
tion).
relationship
rates
pregnancy
report
between
and
will
(l-lolinka
However,
younger
mice.
onset
or
occurred
a smaller
it
Our
of
some
the
is
mice
group.
was
55% less
On the average,
progesterone
older
mice.
levels
A similar
suggested
The
decline
that
eta!.,
progesterone
previous
and
1974;
Michael
decrease
rats
retarded
major
in
eta!.,
and
Zarrow,
mice,
between
plasma
delayed
young
1974;
preparturient
interval
our
cannot
data, since blood
stressful
and
the
the
in
the
relationand
be
was
once.
A pilot study suggested
ing of 11-12-month-old
mice
was
1973),
However,
the
associated
with
At
present,
the factors
controlling
the rate of preparturitional
progesterone
ence
of fetal
of maternal
the inverse
with
number
Because
progesterone
significant
ed
in
the
of
inverse
with
the
significant
decrease
either
and
higher
preparturitional
mothers
lation
with
is also
in
understood.
on the rate
age
in
group,
viable
fetuses
An influof decline
(Table
correlation
of
number
of viable
only
1-2
progesterone
it
days
is unlikely
was
of
plasma
the
fetoplacental
tissues
rat (independent
of the
progesterone
metabolism
in
Maass,
1974)
is consistent
plasma
fewer
fetuses.
This inverse
consistent
with
delayed
progesterone
was
with
progesterone
in
correparturi-
In younger
only) when
correlated
with litter
with gestation
length
it is probable
that
luteolysis
is delayed
C57BL/6J
age-related
changes
of progesterone
clearance
or production from
other
sources
could
also be involved.
The
biological
action
of progesterone
and
other
steroids,
of the hormone,
depends
but
not
also
only on
on target
blood
cell
levels
recep-
tors.
Since
uterine
progesterone
receptor
levels
are regulated
by estradiol
(Milgrom
eta!.,
1973;
Leavitt
et a!., 1974, 1977; VuHai
et al., 1977),
it will be of importance
to correlate
plasma
and
progesterone
with
et al., in preparation),
The
each
progesterone
estradiol
levels
as well as with
receptor
mechanisms
controlling
species
are complex
and
is a considerable
1960;
Fuchs,
1977).
estradiol,
catecholamines
have all been
levels.
parturition
superimposed
oxytocin,
and
fetal
implicated
in
on
species
Proges-
prostaglandins,
adrenal
corticoids
in the regulation
of
by
parturition (Ryan,
1977). In addition, relaxin
appears to inhibit myometrial
activity in mice
3).
and
rats
Paterson,
after
detectthe
(Kroc
1965)
et a!.,
1959;
and
its action
Wiqvist,
on the
1959;
uterus
within
the
hormonal
milieu
necessary
parturition remains to be investigated.
plasma
fetuses
that
correlation
mothers
with
small
litters.
the limited time (Day
18
terone,
of
plasma
progesterone
is suggested
correlation
of plasma
progesterone
the
became
are poorly
components
The
that
complexity
variability
(Short,
increased
luteolysis
decline
(In
viable
fetuses
suggests
that
site may additively influence
that
uteroplacental
sampled
that serial bleedduring pregnancy
abortions.
and
(Egert
uterine
(Holinka
formulated
only
resorptions
luteolysis.
or impaired
in
11-12-month-old
mice in the present study. However,
may
be
parturition
progesterone
of
of
Because
the delayed
preparturitional
progesterone
decline
in aging
hamsters
was
associated
with delayed
luteolysis (Blaha
and
Leavitt,
1975).
Because
progesterone
is
plasma
(Goldman
11-12-month-old
from
preparturitional
are active
plasma
Histodehy-
reports
for
Greenwald,
or
onset
size may make correlation
more difficult to detect.
preceeding
decline
of progesterone
factor
in the
delayed
ships
suggesting
the
uterus)
mice,
generally agreed to be essential for the onset of
uterine
contractions
and
parturition
in mice
and
dence
tion
lagged
trend
was
1969).)
1974),
in
parturition
confirms
mice
(McCormack
major
to
in
progesterone
was
with
prolonged
luteolysis
of
histological signs of luteolysis are
gestation
Day
16 (Choudary
and
progesterone
and
each fetoplacental
in
than
the
(Blaha
and
Leavitt,
1974).
studies of i
-3f3-hydroxysteroid
animals.
a
lagged
on subsequent
days
is significant
groups,
the average
rate of decrease
those
Murr
mice,
by
fetuses
time
the rate of luteolysis, once it is initiated, or of
progesterone
clearance
or
degradation.
Evi-
a decrease
the young,
but
the
decrease
for elevated
preparturitional
found
in some
aging
hamsters
drogenase
the
whether
or whether
with
Although
drop
of plasma
2 days
in the
gestation
chemical
in
resolve
in progesterone
mice
simultaneously
extent.
only
Day
age
viable
the
young
detected
prepara-
levels
on
occurs
in both
do not
decline
in 11-12-month-old
that in the younger
in
in
significant
data
all aged
progesterone
in both
age
net
by
al.,
of
determines
Greenwald,
groups.
in
number
progesterone
be considered
et
The
decrease
in progesterone
17 associated
with
luteolysis
the
litter
ET AL.
a
Many
effect
of the above
at least
levels. Thus,
in
factors
may
part by lowering
injection
of
PGF2a
for
exert their
progesterone
into
pregnant
PROGESTERONE
rats
resulted
in
progesterone,
a marked
AND
decrease
followed
by
PROLONGED
in
of the
prevented
suggesting
the
a!.,
that
primary
1975).
the
cause
delivery
was
of
synthetic
progesterone
the premature
littering,
decline
in progesterone
in initiating
birth
was
(Strauss
et
progesterone
In sheep,
infusion
as
premature
ACTH
of
a common
or
was preceded
progesterone
progesterone
mg/24
(200
the
mother
blocked
induced
parturition
by
the
h) administered
the
(Liggins
(Strauss
decline
et a!.,
dexamethasoneet
al.,
1972).
in
treatment
Because
sheep
1975),
progesterone
did not show
after
(Liggins
et al.,
progesterone
1972).
levels
isms.
Further
alterations
pregnancy
pertains
than to luteotropic
study
in
of
the
causes
mice
ap-
primarily
mechanprogesterone
by means
of the present
help elucidate the control
levels
may
of
rodent
model
mechanisms
of
We express
gratitude
to Kevin Flurkey
for assistance in the collection
of samples,
to Patrick
Randall
for assistance
in analyses
of regressions
and to James
R. Wisner,
Jr. for advice on radioimmunoassay.
This
was
the
supported
NIH
grants
by
(AG-00446,
to
AG-00133,
Caleb
AG-00117
E.
Finch
and
and
NSF
(PCM76-02168)
and by NIMH
Training
Grant
ST22NH0007O.
A part
of this work
was done
with the support
of a Population
Council
Postdoctoral
Fellowship
to Christian
F. 1-lolinka.
in
ability
young.
Biggers,
J.
A.,
Bogart,
R.
and
Sperling, G. (1941). The
upon
the
of the female
rat to reproduce
and raise
Mem. Cornell
Agric.
Expt.
Sta. 283,
26.
D., Finn,
C. A. and McLaren,
A. (1962).
of
age
and
rate
of
breeding
the
factors
163,
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