Quinacrine is a prostaglandin antagonist

Vol. 76, No. 4, 1977

BIOCHEMICAL

AND BIOPHYSICAL

RESEARCH COMMUNICATIONS

QUINACRINE IS A PROSTAGLANDIN ANTAGONIST C.F. Horrobin, M.S. Manku, M. Karmazyn, A.I. Ally, R.O. Morgan, R.A. Karmali Clinical

Received

May

Research Institute & Universite 110 Pine Avenue West, Montreal,

de Montreal Canada

9,1977

Quinacrine, an anti-malarial with local anaesthetic properties, wecause of its fluorescence characteristics and its ability to combine with chromosomes and biological membranes has been widely used as a "probe". The sites with which it combines in Torpedo marmorata electric organs have many of the characteristics of specific receptors. Using rat vascular and gastric smooth muscle we have shown that quinacrine can competitively antagonise We suggest that the biological sites to the actions of prostaglandin E'Z. which quinacrine binds can normally be occupied by prostaglandins.

Introduction Quinacrine Its

(1). (2.3)

is

fluorescence

and to other

rylation

an anti-malarial

and mitochondrial

Torpedo binds the

cholinergic

group

the

"probe".

have led

Using

site.

Surprisingly

the electric

natural

compounds

quinacrine and/or

becomes

local

and procaine)

behave is It

sites,

interacts

substances

are normally

sites

has been shown of combining a

prostaglandin

a prostaglandin

and possibly

of

(including

to chloroquine

is

behaviour

We have shown that

as competitive

too

of

quinacrine

the

be capable

attached.

related

extensive organs

interest

might

anaesthetic

Quinacrine

the membrane

little

phospho-

to its

can modulate

and properties.

quinacrine

(6,7)

which

(10,11,12).

which

activity

of oxidative

receptor

antagonists

with

inhibition

allosteric

quinine

that

to chromosomes

have shown that

of anti-malarial

We propose

to bind

ability

(8,9)

to which

in structure

properties

& Changeux

chloroquine,

both

anaesthetic

Grunhagen

as to what

sites

local

its and its

ATPase

receptor

question

(4,5)

and membrane

to a specific

in the with

marmorata,

with

characteristics,

membranes

use as a chromosome

drug

the nucleic to which

and quinine antagonist. acid

sites

prostaglandins

can bind.

Copyright All rights

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

1188 ISSN

0006~291

X

Vol. 76, No. 4, 1977

BIOCHEMICAL

Flaterials

AND BIOPHYSICAL RESEARCH COMMUNICATIONS

and Methods

Yost of the experiments were carried out on the perfused superior mesenteric artery of the male rat as previously described in detail (13,14). Under ether anaesthesia the artery was cannulated and its vascular bed dissected out and mounted in an organ bath. Using a peristaltic pump the preparation was perfused with Krebs-bicarbonate buffer at a flow rate of 3 ml/minute. Perfusion pressure was recorded via a side arm off the arterial cannula. Test injections into another side arm of pressor agents dissolved in 0.1 ml buffer caused brief vasoconstriction and hence elevation of pressure. We have previously shown that both the baseline pressure and the responses to a fixed dose of pressor agent remain stable for many hours. Actual doses of pressor agents used, each sufficient to give a 40-60% maximal pressor response were 10 ng noradrenaline as the bitartrate, 7 micromol of potassium chloride, 1 ng of angiotensin II and 25 ng of The pressor effect of potassium injections synthetic arginine vasopressin. is not dependent on release of noradrenaline from nerve endings since it persists even after complete abolition of adrenergic effects by phenoxybenzamine. Responses to potassium and vasopressin are rapidly abolished by the use of a calcium-free buffer and presumably depend on stimulation of calcium entry from outside. Responses to noradrenaline and angiotensin remain at 60-80% of their original level on removal of extracellular calcium and presumably largely depend on calcium release from intracellular stores. In two experiments the effects of quinacrine on contractile responses of rat stomach strips were investigated. We tested the actions of quinacrine on pressor responses to noradrenaline, and potassium ions (6 experiments each) and to vasopressin and angiotensin (2 experiments each), Once the preparation had stabilized, three test injections of the pressor agent to be used were given: the mean amplitude of these responses was taken as 100% and subsequent results were expressed as percentages of this. Progressively increasing concentrations of quinacrine were then added to the buffer each beino present for 10 minutes: at the end of that time the response to the same fixed dose of the pressor agent being used was tested. Preliminary experiments had shown that changes in response to a given concentration of quinacrine reached a plateau within 5 minutes and thereafter no changes occurred in spite of maintenance of the same concentration of quinacrine for prolonged periods. Results Within in the

the 10m6M range

amplitude

inhibition against

of pressor

was obtained noradrenaline

we showed

that

the

of noradrenaline that

of potassium

than inhibition ones while

responses 1). against

caused but

in the

Quinacrine

consistent

10w5M range

was rather

potassium.

of angiotensin that

a weak but

consistent

more effective

In two experiments responses

of vasopressin

increase

was similar

responses

each to that

was similar

to

ones.

We have previously of prostaglandin

(fig.

quinacrine

shown that

antagonists

a characteristic

on vasoconstriction

1189

of the is

that

inhibitory

the adding

actions of

Vol. 76, No. 4, 1977

BIOCHEMICAL

'E;,, \t \

2 l&l a 60P 40 it? it? I

40

g

20-

AND BIOPHYSICAL RESEARCH COMMUNICATIONS

k,

-

0-l -

NORADRENALINE POTASSIUM CHLORKE

0--

NORADRENALINE

\ “Yf\*

B s Qz

\

0’

0.2

0.4 lbhi

0.8

I6

QUINACRINE

'

+

3.2

64 4 lO+M

12.8

CONCENTRATION

\

’

\

25.6

51.2

&g/ml

1:

The effects of increasing concentrations of quinacrine in the perfusion amplitude of the pressor responses to fixed doses of noradrenaline (10 ng) and potassium ions (7 ~~mol) injected in 0.1 ml buffer. Results are expressed as percentages of the responses to three pressor injections prior to addition of quinacrine to the buffer. Each pressor agent was tested on 6 preparations and the results show the mean GEM at each point.

+f u;d on the

indomethacin glandin

(5 us/ml)

synthesis

of exogenous

In three

moves the

prostaglandin

experiments

pressor

agent

influenced

either test

the buffer sections 5 rig/ml

both

graph

prostaglandin

strips

the

inhibitory

E2 is

parallel

of rat

stomach

the

right

(10,15). as the

of quinacrine

and prostaglandin

were

given

the

to and to the

1190

partially

restored At this

right

the

inhibitory of that

in an organ

by

stage

added

Comparing

can be seen that

mounted

(64 pg/ml)

and quinacrine

as before.

Finally

and vascular

of indomethacin

buffer.

is

E2.

synthesis

then

prostaaddition

noradrenaline action

E2 to the

were

while

to the

using

were

concentrations

endogenous

left

prostaglandin

prostaglandin

2) it

it

shown)

to noradrenaline

(fig.

to the

pushes

concentration

of noradrenaline

to inhibit

not

endogenous

1 or 5 rig/ml

of the

that

a high

in increasing

Isolated

(results

Responses

injections

line

way by indomethacin

by adding

to the buffer.

partially

inhibitory

we demonstrated

responsiveness

three

each

blocked

buffer

E2 (5 rig/ml)

in a similar

we completely

adding

to the

bath

to

linear line

with

and

with 1 rig/ml.

Vol. 76, No. 4, 1977

BIOCHEMICAL

dp

AND BIOPHYSICAL RESEARCH COMMUNICATIONS

I20 -

z z 0 a9

100 < 80-

2 2

60-

2 2

40-

a w Y

20-

8

a

t Snghl

.

INDO

0

/ND0 +lng/ml

PGEp PGE2 \

02

z

1.6

0.4 08 4 IO-6M

OUhVACRlNE

3.2

6.4 4 IO-%4

CONCENTRATlON

128

256

kg/m/

Fig. 2: The effects of increasing concentrations of quinacrine in the perfusion fluid on the amplitude of responses to 10 ng noradrenaline when the perfusing buffer contained 64 pg/ml indomethacin and either 1 or 5 ngl The indomethacin abolished endogenous prostaglandin ml prostaglandin E2. synthesis and also vascular responsiveness. Responsiveness was partially three control injections of noradrenalir restored by the exogenous prostaglandin, and then quinacrine was added to the buffer. 6 experiments were were given, done with each prostaglandin concentration and the results are shown as mean GEM.

responses curves

measured using

in control

increasing buffer

the

right

an isometric

buffer

quinacrine but

did

recording

concentrations

and in

two experiments to the

using

not

system.

of prostaglandin

containing

change

the

E2 were

5 or 10 pg/ml

moved the dose/response amplitude

Dose/response

curve

obtained

quinacrine.

In

progressively

of the maximal

response

to

prostaglandin.

Discussion A peculiarity synthesis

on the

constrictors produce

rat

appear

mesenteric

of the action

of drugs

which

preparation

is

to be blocked.

a 50% inhibition

irrespective glandin

of the action

of pressor pressor

such as local

agent

The drug response used

(14).

anaesthetics

1191

inhibit that

prostaglandin responses

concentration is approximately Some antagonists

and methyl

xanthines

to all required

vasoto

the same of prostabehave

in a

Vol. 76, No. 4, 1977

similar

BIOCHEMICAL

way (10,15).

inhibitors

buffer

vascular

reactivity.

adding

present

still

inhibit

moves it

in preparations

restored

to the

with

synthesis by exogenous

preparations

left

while

3. It

right.

a high

and vascular prostaglandin

with

5 or 10 ug/ml E2

1 rig/ml

moves the on rat

stomach

enhancement

explanation

for

Since

in the

of the pressor

ions

reactivity

range

prostaglandin

local

probably is able

In the

5 rig/ml in relating

to inhibit

responses.

moves the E2

to noradrenaline

to abolish

endogenous

responsiveness

was

indomethacin-E2

treated

E2 was parallel

and to the

a concentration

of either

the effect

progressively quinacrine

of a

prostaglandin

responses

whose

anaes-

and vasopressin.

dose of indomethacin

curve

synthesis

by indomethacin

pressor

contractions 10%

but

other

of extra

5. Quinacrine

strip

like

1. It

addition

with

the indomethacin

agents.

synthesis

4.

by

of prosta-

to the

caused

right.

a slight

but

At the moment we have no

this.

quinacrine

chromosomes

E2.

dose/response

In concentrations consistent

curve

blocked

potassium

E2.

be restored

antagonist,

antagonises

the dose/response

of that

already

as follows:

angiotensin,

treated

prostaglandin

is

and

of prostaglandin

quinacrine,

of prostaglandin

curve

to the

that

in the

synthesis

even with

a prostaglandin

The evidence

inhibition

dose/response

glandin

is

is

and

indomethacin

can then

buffer

to pressor

suggest

antagonists

sufficient

inhibitors

synthesis

to noradrenaline,

2. Partial

prostaglandin

reactivity

situation

responses

strongly

type.

responses

right

that

RESEARCH COMMUNICATIONS

prostaglandin

E2 to the

and anti-malarials,

competitive

vascular

In this

because

Our results thetics

endogenous

Normal

(14).

antagonists

both

prostaglandin

have no effect

between

can be made by using

to block

exogenous

still

A distinction

of synthesis

perfusing

AND BIOPHYSICAL

is

and membranes

a prostaglandin with

by prostaglandins.

Prostaglandins

membrane

acid

and nucleic

which

antagonist, quinacrine may play

function.

1192

the

interacts an important

binding

sites

may also part

on

be occupied

in regulating

Vol. 76, No. 4, 1977

BIOCHEMICAL

AND BIOPHYSICAL RESEARCH COMMUNICATIONS

References 1.

Thompson, P.E. and Werbel, L.Pl. 185, Academic Press, Ilew York.

2.

Caspersson, Simonsson,

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L.,

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Wagh,

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Caspersson, Simonsson,

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D.F. D.F.

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and Hamet,

789-801.

1115-1117.

(1976).

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J.

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369-376.

P. (1977).