which reached nondetectable concentrations within. 24-48 h after implantation of the. T capsules. This rapid suppression of LU secretion induced by. T treatment.
BIOLOGY
OF
REPRODUCTION
Testosterone
32,
(1985)
1109-1115
Administration
(Macaca
to Ovariectomized
Female Rhesus of Pulsatile
Monkeys
mu/atta) Reduces the Frequency Luteinizing Hormone Secretio& A.
K.
and
DUBEY
Department
T. M. PLANT2
of Physiology
University
of Pittsburgh
School
of
Pittsburgh,
Medicine
Pennsylvania
15261
ABSTRACT In the
male
rhesus
monkey
testosterone
(T)
retards
the
frequency
of intermittent
LH
secretion.
The purpose of the present study was to determine whether this action of T is demonstrable in the female. Five ovariectomized rhesus monkeys, bearing indwelling cardiac catheters, were implanted s.c. on one or more occasions with T-containing Silastic capsules. Sequential blood samples were collected for 8 h every 10 mm before T treatment and usually at 1, 2, 4, and 8 days thereafter. Plasma LH concentrations were measured in duplicate by radioimmunoassay and subsequently analyzed with a computerized algorithm. Sustained increments in circulating T (5-13 nglml) in ovariectomized monkeys resulted in a progressive reduction in LH pulse frequencies from approximately 1 pulse every 60 mm before initiation of T treatment to 1 pulse every 100-150 mm at 48 h thereafter. In most cases the deceleration in pulsatile gonadotropin secretion continued, and by 4-8 days of T treatment LH pulse frequencies as low as 1 pulse every 5 h were observed. The onset of the T-induced deceleration in LI-I pulse frequency was generally associated with an increase in LH pulse amplitude and with a decline in mean LH levels. This LH response in the female to T treatment
was
similar
to that
previously
reported
for
INTRODUCTION
In (T)
several administration
tion
D’Occhio the
acutely
mals
1982;
in 1
discharge
within LH
T-containing
observed
in
24 to 48
pulse every
frequency 2
h
intact
In
the
LH
(see
of
T would
pulse
generator.
GnRH
pulse
to
This
ability
to
was
secretion sumably
in
female
the
decelerating
by
determine the
rhesus
of
GnRH
the GnRI-1
modulate the
major
feedback
testes
animals,
influence
MATERIALS
the whether
monkey,
be
negative
purpose
ovariectomized
therefore
the
of T to
the
at of
governs
so-called
to
fore-
exerted
frequency
that the
seems
The
the
be
the
GnRH,
frequency
1984).
study
Accepted January 21, 1984. Received September 28, 1984. ‘This research was supported by NIH grants HD1685 1 and HD-08610. A preliminary report of this study was presented at the 17th Annual Meeting of the Society for the Study of Reproduction, Laramie, WY, 1984 (Abstract 5). 2Correspondence (412/624-0260).
of
of LH secretion
Dubey,
1982).
1983a),
seem
underlying
control
to approxi-
hormone
Plant,
of the brain to retard neural timing mechanism release
reof
to
pattern
level
mechanism
male
is considered
intermittent
gonadotropin-releasing
pulsatile
circu-
secretion
secretion action
the
h, in a marked (Plant,
pulsatile
a corresponding
going
Silastic of
Since
flect (GnRH)
monkey,
concentrations
to those
results,
deceleration
rhesus
of
produce
similar
monkeys
1982).
castrates.
hypothalamic
a reduc-
of approximately 1 disreported, and in such ani-
implantation that
in
et a!.,
orchidectomized
s.c. T
results
Steiner
pulse frequency per h has been
capsules
lating
males
testosterone
of intermittent luteinizing secretion (Santen, 1975;
et a!.,
an LH charge
species,
to
frequency (LH)
in
hormone
mately
mammalian
male
the
(Plant and present
episodic and
LH pre-
pulse
generator
of
is also
responsive
to
of T.
AND
METHODS
Animals Five adult female rhesus monkeys (5.2-6.9 kg body weight) were used in these studies. The general maintenance of the animals under a controlled photo-
1109
DUBEY
1110
period
(lights
scribed
previously
Surgical
on
from (Krey
0600 to 1800 et al., 1975).
h)
has
AND
been
de-
Procedures
In
order
to
without
restraint
planted
via
sequential
or tranquilization,
a jugular
vein
with
blood
animals a chronic
samples
were
im-
indwelling
of Blood
For the description of pulsatile profiles of plasma LH concentrations, blood samples (1.1 ml) were withdrawn via the cardiac catheter every 10 mm for 8 h during the light phase of the 24-h light-dark cycle as previously described (Plant, 1981). Plasma was stored at -20#{176}C until required for assay and red blood cells were returned to the animals after they had been resuspended in 0.9% physiologic saline. Radioimmunoassays Luteinizing hormone was estimated usually in dupby a cynomolgus LH-antihuman chorionic gonadotropin (hCG) (rabbit 13, pool D) radioimmunoassay (RIA) system that employs a rhesus pituitary preparation (WP-XV-20, NICHD-rhLH) as standard. This RIA is distributed in kit form by the National Hormone licate
and
Pituitary
Program
and
(Peckhani and Tontala, LH assay ranged from Plasma T concentrations viously described RIA (Plant et al., 1978). Analysis
and ketamine Parke-Davis,
of Pulsatile
LH
has been described in brief 1981). The sensitivity of the 10 to 15 ng WP-XV-20/ml. were measured by a prethat utilizes antiserum S-250
tions
into
adult
male
1981). before 8 days
the
was
those
observed in intact 10-20 ng/ml (Plant, were collected 2 days cases, at 1, 2, 4, and of animals, T treat-
i.e.,
withdrawn
and
Initiation
of
the
first
after
a further
period
in ovariectomized
rhesus
marked
in LH
reduction
(#1209
and
third
#1416)
animal but
ber
of
which
The animal
12-32
time
a
frequency animals
(#1276
treatment
after
an
with
of
circulating
tion
peated ber
the
in these of
results
two
were
capsules.
again
obtained. two
Silastic
capsules,
course from
with
therefore a smaller
However,
During
animals,
T treatment
of
patterns
was
these
in
induced
time
concentrations animals
which
T capsules.
secretion
the
T by
within
of the LU
experiment
T-containing
periment
LH,
moment-to-moment
LH The
two of
followed
plasma
prevented
pulse
initiation
concentrations
treatment
monitored.
LH
remaining
was
in
numduring
in
ovariectomy
h after implantation rapid suppression of in
a greater
#1361),
decline
first
therefore
capsules,
In the
nondetectable
the
in was
reduction
and
in a in two
animals. In a of T was also
than
Silastic
observed.
immediate
reached
#1086
treatment
frequency
degree
distinct
was
T
resulted
experiment
containing
T
pulse
a lesser
to
two monkeys. repeated in
of
monkeys
of the five this action
(#1086),
changes
described
of
RESULTS
any
have been
range
monkeys,
1 day before and 1 day after the implantation of empty Silastic capsules in one animal, a systematic evaluation of the effects of blank implants on momentto-moment changes in plasma LH concentration was not conducted. Instead, the influence of possible nonspecific effects associated with capsule implantation and repetitive sequential sampling on pulsatile LH secretion were further assessed in the following ways. In one monkey, sequential blood samples were collected 1 day before bilateral ovariectomy and at 2, 4, and 10 days thereafter, and in another animal sequential blood samples were collected 1, 2, 5, and 8 days after the withdrawal of T on Day 17 of steroid treatment, on each of two occasions.
T
al., 1973b), as has the et al., 1973b; Plant et while the animals thiamylal (40 mg BioInc., St. Joseph, MI)
i.m.;
were implanted with 12-2 5 days after castracirculating T concentra-
blood samples and, in most In the majority
then
by
capsules
upper
rhesus
Testosterone was administered by s.c. implantation of 4-cm long Silastic capsules (3.5-9 capsules/animal) made from Silastic medical grade tubing (DowCorning, Midland, MI; i.d., 0.132”; o.d., 0.183”) containing crystalline T. The construction and preincuba-
of steroid-containing
Ketalar
without steroid treatment the experiment was repeated. In two animals, the withdrawal and reinitiation of T treatment was repeated for a third time. Although sequential blood samples were collected
This
in detail previously (Karsch et method of implantation (Karsch al., 1978), which was performed were anesthetized with sodium tal i.v.; Bio-Ceutic Laboratories,
mg
days
24-48 Treatment
monkeys capsules to elevate
Sequential T treatment thereafter.
ment
(100 NJ).
Protocol
Ovariectomized T-containing Silastic tion in an attempt
evident, Profiles
A computerized algorithm (PULSAR) developed by Merriam and Wachter (1982) for pulsatile hormone analysis was used to determine LH pulse frequency and amplitude. The criteria employed in the present study to define an LH pulse were identical to those used in a previous investigation of the effects of T replacement treatment on pulsatile LH secretion in acutely orchidectomized rhesus monkeys (Plant, 1982). Testosterone
hydrochloride Morris Plains,
Experimental withdraw
18- or 19-g polyvmnylchloride cardiac catheter and subsequently housed in a remote sampling cage as previously described (Plant, 1981). Bilateral ovariectomy was performed under sodium pentobarbital anesthesia (Nembutal; Abbott Laboratories, North Chicago, IL; 30 mg/kg body weight i.v.) usually 2-3 wk after placement of the cardiac catheter. However, one animal was gonadectomized at the time of catheterization. Collection
PLANT
with
was
being renum-
similar a third exstill fewer
followed
by a
T RETARDS
striking reduction LH secretion. The results of
one
the
in
five
animals,
biguous
T
1, and
phenomenon 1 and
PULSE
FREQUENCY
pulsatile
from
each of an unam-
induced
pulse
frequency,
representative
are Prior
2.
of
experiment in LH
in Table
this Figs.
frequency
which
deceleration
shown of in
in the
LH
are
IN FEMALES
sules was the result of a feedback steroid, and not a consequence effects associated with implantation tive sequential T-containing blank
examples
graphically presented to T treatment, LU
1111
blood Silastic
implants
LH pulse removal
in
sampling. capsules,
In
animal
did
one
frequency 24 of T capsules
studied resulted in a prompt fast LU pulse frequency that
discharge
the
of
LH
in the
open
reduced
of exposure to plasma by 4-8 days of such frequencies as low as observed.
In
three
reduction in LH with a suppression (Table
1).
in LH
pulse
with
2
days
the
five
animals,
the
onset
of
the
was
increase
in LU
pulse
LH
interpulse
interval
and 24 h after implantation capsules in one animal was 57 ± 24 mm, respectively. withdrawal on LH secretion two
occasions.
removal
identified
of (on
On
the
the
T implants,
one
day
largely
were undetectable) of 118 ± 47 mm.
drawal,
LU
IPI
24 h on one within 5 days pulse frequency sustained (8 days). detectable animal
decreased
plasma
studied
to 56 ± 18 mm
duration of the LH concentrations to ovariectomy in
this
however,
200.0 mm of pulsatile
were identified, LH release was
pulses; IPI 78.0 IPl 44.1 ± 13.3
tomy. that
The acceleration in LH followed ovariectomy ng/ml
to
rise 111
±
± 8.4 mm) mm) days
in mean 22.8
and 10 postgonadec-
pulse was LU
ng/ml
levels by
viously
10
DISCUSSION of
evidence
suggest
inhibition of pulsatile LU secretion lowed implantation of T-containing
that
the
that Silastic
folcap-
Decker
et
demonstrated
(Gay changes
and in
the
present mized
results that of
intact
adult
reduction
ovarian thecoma
mation premature
LH
this
secretion
This
to
the
been
the
in
of I concentra-
range
date,
observed
in
at variance
women from
with hyperpolycystic
et al., 1984)
ovarian circulating 1976;
Baird
and,
although
however, that
in
elicits a striking of pulsatile LU
and steroid-secreting modestly elevated
to
of The
ovariecto-
is seemingly
(Rebar et a!.,
rat
evaluated.
that,
that resulting
et
concomitant fluctuations
administration circulating the
a
pre-
ovariectomized
not
into
conclude
T,
negative
has
1981),
documented, an enhanced (Rebar et a!., 1976). With available
by
the
al.,
finding
disease exhibit
filled
gonadotropin 1972; Plant
males (Plant, 1981) in the frequency observations states
capsules
was that
regulates (Lee et al.,
were
steroid
of secre-
interpretation that an incre-
of
elevate
concentrations 1977; Dunaif
less well frequency
of
monkeys,
quantities tions
Silastic
demonstrate
rhesus
LU
of this steroid in LI-I secretion
of
in
release
effect
pulsatile
Uauger, 1977), moment-to-moment
gonadotropin
LU a!., lines
1978;
that male
substitute
of
component
loop in the
with the androgenic
postcastration.
Three
testicular
secretion.
from Day
implantation androgen. an inhibition
10
associated
LH pulse frequency. observations, albeit
on
followed with this While
LU was
frequency associated
the of
2, 4, and
was
a sufficient
capsules
T or a metabolite for the changes
a!.,
(11
are
ment in responsible
mm
at
Days
tion. Thus, the less circumspect of our results is merited, namely,
feedback secretion
experiments were unin the one
of
in a mainte-
animal
examination
blank
major
within
and the frequency further increased
4 (6 pulses;
a progressive
with with-
regard. By Day 2 post2 LU pulses with an IPI of
castration,
