Reduced nuclear triiodothyronine receptors in starvation-induced hypothyroidism

BIOCHEMICAL

Vol. 79, No. 1, 1977

AND BIOPHYSICAL RESEARCH COMMUNlCATlONS

REDUCED NUCLEAR TRIIODOTHYRONINE IN STARVATION-INDUCED Leslie

J.

Hisao

DeGroot,

Seo,

Thyroid

Aldo

Enio

Study

University

Received

August

HYPOTHYROIDISM*

H. Coleoni,

Martino, Unit,

Paul

and Samuel

Department

of Chicago, Chicago,

RECEPTORS

Refetoff

of Medicine,

950 East

Illinois

A. Rue,

59th

Street,

60637

12,1977 SUMMARY

Starvation of male rats during 48 hours causes a marked reduction of serum thyroxine, serum triiodothyronine, and liver nuclear triiodothyronine content. Liver nuclear receptors capacity for binding of triiodothyronine was reduced, in contrast to thyro-previc hypothyroidism in which binding capacity is normal. DNAdependent RNA polymerase activities were reduced. In contrast to typical hypothyroidism, serum thyrotropin was low. This form of pituitary non-responsive hypothyroidism may represent a selective response to caloric and/or amino acid deprivation. INTRODUCTION Acute

starvation

This

effect

sion

of thyroxine

formation hormone serum

explained (T4)

of 3, 3', levels

insulin

increased lead

is

nuclear

levels

We have shown

that

Supported AM-15070.

insulin

is

receptor

receptor

T3)

capacity.

(4).

capacity

induced

(3).

Alteration

ndividuals High

converincreased in serum

reduction leads

of

to

serum prolactin

levels

It thus becomes of interest

(5).

reduction

and possibly

For example,

of obese

capacity

(1 - 3).

in peripheral

( T3),

(reverse

receptor

starvation

of serum T3 is

associated

with

capacity.

known about

T3 binding

by United

by a reduction

by starvation

T3 receptor little

in part

cell

induced

whether

serum T3 in man and rats

to 3, 5, 3'-triiodothyronine

prolactin

To date

*

at least

may modulate

to augmented

altered

known to reduce

5'-triiodothyronine

membrane

to determine

is

States

Copyright 0 1977 by Academic Press, Inc. All rights of reproduction in any form reserved.

capacity Public

the

physiology is not

Health

altered

Service

of nuclear

T3 receptors.

by hypothyroidism Grants

AM-13377,

or CA-19266,

173 1SSN

0006-291X

and

CI 2

C

25.8

24

24

48

9.8

*

*

assayed

Different

in triplicate.

from 0 hour

control

with

each group

D, n = 3 with P <

x 10-'5M/100

were

group.

were

4.1

2.4

2.7 3.1

f

l

f

6.1

2.9

3.5

f 9.4 f 11 f 10.2

f

f

f f

*

*

*

were of two livers.

animals

All

pools

animals

.ll

.14

T3 rig/g

were

individually

in triplicate.

in triplicate.

in triplicate.

.40 l

.51 f

.65 * .16

.69 + .03 * .64 f .ll * .51 * .lO *

.79 f .03

Serum w/ml

done on each pool done on individual

Assays

done on individual

deviations.

50.8

52

60.1

46.4 55.9 38.4

54.3

50.1

51.9 52.4

i- 11

Total

ug DNA

63.1

of a pool

assays

each

assays

.05.

consisting

and all

for

and all

pooled

In Experiment

were

B, three

C, n = 6 in each group,

In Experiment

In Experiment

A, n = 3 in each group,

livers

Capacity

BINDING CAPACITY AND T, LEVELS .J

Data are means f standard

f 2.7 *

* 2.3 *

k10.3

f 8.1

l 12

l

* 3.4

In Experiment

are presented.

46.2

0

Four experiments

34.5 38.8 24.1

12 24 48

42.1

20

40.4

41

0

59.7

0

f 1.3 *

14

f 2.1

16.5

20.2

48

A

Nuclei

1.5.8 f 2.3 14.8 f 1.0 *

0

Expt.

13 Binding

12 24

Hours of Fasting

1

f

.43

.45 f .24

.12

* .54 .61 f

1.15

.84 i .05 .77 f .14 * .78 i- .23 *

1.40

Liver Nuclei Tissue Equivalent

3 v,

F

$ 5

8

P

i? v, F

P

Fi 9 s

> 5

su

.

0

-3 z

< 0

Vol. 79, No. 1, 1977

BIOCHEMICAL

AND BIOPHYSICAL RESEARCH COMMUNICATIONS

TABLE 2 DNA DEPENDENT RNA POLYMERASE ACTIVITY: Hours Experiment

of Fasting

Total

.186

f .OOl

I

.038

l

* .003 *

.118 ) .003 *

.025

20

.115

.019 f

* .OOl *

.002

.002 *

C: 0

.14 f .02

.021

12

.12 f

.013 f

24

.09 * .Ol *

.OlO * .OOl *

48

.09 f .Ol

.OlO f .OOl *

*

Different

Experiments

exposure

in neonatal

capacity

Polymerase

14

Experiment

Estrogen,

Polymerase

B: 0

acute

FRACTION CTP BOUND/mg DNA

from 0 hour are

to exogenous

male rats; glucocorticoids,

control

as described

T3 (6).

capacity

.02

* with

in Table

P <

to adult

and testosterone

.OOl *

.05.

1.

We have reported

rises

f .005

levels

low nuclear

binding

by age 30 - 50 days

had no effect

capacity (7).

on T3 binding

(7). METHODS

Male Charles River Farm rats having Purina rat chow continuously Animals were housed on screen floor

of 150 - 220 g body weight were studied while available, or while fasted for 12 - 48 hours. cages, and were given tap water ad lib.

At the desired interval animals were sacrificed by stunning or by exsanguination through cardiac puncture under light ether anesthesia. Serum was analyzed for T (8), T (9), TSH (lo), and total serum proteins. T3 binding capacity of liver 4 uclei, ft.inding affinity of receptors for T nuclear T content, and liver nuclear DNA-dependent RNA polymerase (total and Po&erase I) w&-e determined as previously described (11, 12). Protein was assayed by the method of Lowry et al. (13) and DNA by the method of Munro and Fleck (14). Statistical compassG'is were made using a Student "t" test for unpaired data. Means, standard deviations, and statistical significance are given in all tables.

175

Vol. 79, No. 1, 1977

BIOCHEMICAL

AND BlOPHYSlCAL

RESEARCH COMMUNICATIONS

TABLE 3 HORMONE AND PROTEIN LEVELS SERUM Hours of Fasting

Qs/:BO

0

4.0

Total Protein (g/100 ml)

ml)

TSH (fig/ml)

Pituitary TSH pg/gland

f 0.8

6.1 f 0.3

80 f 47

1155 f 75

24

3.7 * 0.5

5.9 f 0.2

27 zt 16 **

1116 f 56

48

2.8

5.8

<20

* 0.6

*

f 0.6

*

**

961 f 64

P(O.05

** P(O.005 Data are

from

Experiment

D

RESULTS r3 Receptor

Capacity

In four

separate

in mean binding

1) --

experiments,

capacity.

statistically this

(Table

The mean level

significant)

time

period.

starvation

in three

After

48 hours

was reduced

studies T3 binding

18 - 48%, and the reduction

was statistically

The reduction

in the

receptors

and in total

receptor

of in vitro released Table Nuclear

to the

Liver

incubation

1 as "total"

Activity

total

(Table

polymerase

of starvation I)

medium

capacity

in nuclei

in vitro

assay.

and were

after

significantly

reduced

diminished by 35% (total)

at the

end

receptor (Indicated

in

after

12

and 52%

48 hours.

of liver

nuclei

(Tables fell

1, 3) -within

176

12 hours

by

experiments.

2) -I activity

not

was reduced

in all

including

(but

were made at

in the nuclei

capacity,

the

and Polymerase

and Serum Hormone.Levels T3 content

during

observations

present

reduction

by 12 - 14 hours

in which

significant

with

receptor.)

Polymerase

(Polymerase

both

incubation

Both hours

occurred

was associated

and was depressed

by

Vol. 79, No. 1, 1977

BIOCHEMICAL

45 - 61% at 48 hours. depression

AND BIOPHYSICAL RESEARCH COMMUNICATIONS

Serum T3 was likewise

of 49 - 60% by 48 hours.

decrease

in serum

T3, and both

T4 declined

at 12 hours,

The decrease

exceeded

Serum T4 and TSH dropped

lower

the

decrease

dramatically

by 31% and TSH more than

in liver

reaching

T3 exceeded

in T3 receptor

during

48 hours

75% at 48 hours.

a the

capacity.

of starvation.

Serum proteins

were

not altered.

DISCUSSION Our studies with

starvation

during

in rats

of nuclear

reported

this

and nuclear activity

response

depression

and depression

We show that

T3 content

to the usual

of serum T4 observed

is associated

T3 receptor

is also

in serum T3

a significant

capacity.

sharply

in hypothyroidism,

with

Nuclear

DNA

In striking

reduced. serum TSH is

reduced

rather

elevated. Physiolog

Animals were

(2).

RNA o f polymerase

dependent contrast

the previously

in man and in the rat,

fasting

lowering

than

confirm

lost

c primacy

then,

altered.

by a cessation

the changes

caloric

acid

The decrease of starvation, receptors

rather is

While

function

both

between

these A tenable

selective

it

fast,

but serum

presence

a selective

proteins

of considerable

much faster

hormone

a response

normal

than

synthesis.

could

Most

physiologic

our

parameters

to lowering

be

likely,

response

to acute

data

do not prove

is that a cause

despite reduced

effect

since

even

the T3

lower

in hypothyroid

receptor

content

and effect

serum animals

and polymerase

relationship

starvation.

is that

responses

interest

an independent

of serum T3,

animals,

RNA polymerase

of great

during

hypothesis

represents

in hypothyroid

is obviously

physiologic

T4 fell

probably

DNA dependent

decline,

the

to be determined.

deficiency.

than

capacity

despite

3).

represent

in T3 receptors

T4 and T3 levels. (12).

(Table

remains a 48 hour

of intrathyroidal

observed

and amino

during

Serum TSH fell

in the pituitary

explained

variables

16 to 20% of body weight

minimally

TSH reserves

among these

the

changes

designed

177

observed

to induce

represent

a state

a group

of "pituitary

of non-

BIOCHEMICAL

Vol. 79, No. 1, 1977

responsive

hypothyroidism"

T3 and T4 during teleologic this

and to protect

acute

caloric

hypothesis,

form

it

of this

to the diminished

is possible in the

acid

from

the

deficiency.

to directly fasting

hypothesis

caloric

tissues

and amino

of hypothyroidism

Extension

AND BIOPHYSICAL RESEARCH COMMUNICATIONS

test

While the

effects this

possible

of

is a value

of

animal.

to man may be logical,

expenditures

catabolic

observed

during

and may be related human fasting.

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