Luteinizing Hormone Secretio

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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,

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