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Effect of melatonin on uterine contractility
Life Sciences Vol . 4, pp . 1367-1372, 1965 . Great Britain.
Pergamon Press Ltd.
Printed in
EFFECT OF MELATONIN ON UTERINE CONTRACTILTTY* Margalit Hertz-Eshel** and R. Rahamimoff The Department of Physiology, Hebrew University Hadassah Medical School, Jerusalem, Israel
(Received 12 May 1965)
Since the isolation of melatonin (5 Methoxy-N-Acetylti~yptamine) from the pineal body in 1958 by Lerner at al . (1) and the discovery of its enzymatic synthesis from 5-hydroxytryptamine (serotonin) in the same organ {2, 3), there has been increasing interest in the function of this substance. Melatonin inhibits the spontaneous motility of isolated rat duodenum and abolishes the 5-hydroxytryptamine induced contractions of this preparation {4).
It has also been observed that melatonin decreases the exci-
tability of frog sciatic nerve in vitro (5). Furthermore, it has been shown that m~~latonin has a definite effeet on the female rat genital system, causing a decrease in the incidence of oestrus, following intraperitoneal or subcutaneous injection (6, 7) and
* Com-nunicated to the 5th Scientific Meeting of the Israel Physiological and Pharmacological Society . Nes-Ziona, 23rd February l~fi5 . ** Part of M. Sc . thesis . 1367
1388
EFFECT OF MELATONIN
interfering with growth and maturation of the ovary (8).
Vol. 4, No. 14 Melatonin also de-
creases the seminal vesicle weight in male rate (9). In view of the inhibitory effect of melatonin on excitable tissues and its action on the female genital system, we thought it desirable to study the effect of melatonin on the activity of uterine smooth muscle . Materiale and Methode Female rats of Sabre strain (80-100 grams) were treated for three days with a daily dose of 50 ~tg~100 gr body weight, diethylstilbestrol previou~ to the performance of the experiments in order to sensitize the uteri. The animals were sacrificed by stunning and cervical fracture and the uterine horns were dissected out. The uteri were mounted vertically in a bath containing Krebs-Ringer bicarbonate solution (10) at 37°C through which a gaseous mixture of 95°Jo oxygen and
5°Jo C02
was bubbled.
The contractions were recorded isotoni
cally on a Kymograph or isometrically with a force displacement transducer (FT03) on a polygraph (Grass 5P).
The preparation was allowed to equilib-
rate for 30 minutes before addition of serotonin (5-hydroxytryptamine creatinine Sulphate - Light and Co . Ltd . Colnbrook, England) or melatonin (Regis Chemical Co ., Chicago, IIl., U. S. A.) or a mixture of these two compounds . The results presented here are based on 78 experiments done on 40 rata .
Each uterus served as its own control since some variability in
amplitude and frequency of contractions was observed .
Vol. 4, No . 14
EFFECT OF MELATONII3
1369
Results (1) Inhibition of Spontaneous Contractions On addition of melatonin at a final concentration of ~0 X 10
-9
moles f
/ml to uteri contracting spontaneously, a slit inhibition of the contractions is observed . -9
160 X 10 X 10
-9
When the concentration of melatonin is increased to
moles f ml the inhibition increases. A concentration of 300 X
moles/ml completely inhibits the spontaneous contractions (Fig . 1) .
a. 160 nM/ml Mtlctonin
300
nM/ml
Melatonin
1 min
FIG. 1
Inhibition of spontaneous contractions rat uterus by melatonin
1370
EFFECT OF MELATONIN
Vol. 4, No . 14
(2) Inhibition of 5-hydrox~rtryp tamine Induced Contractions 5-hydroxytryptamine, which is one of the most potent contracting agents for uterine smooth muscle, is related chemically to melatonin. The mutual relationship of these two substances on the uterine motility has therefore been examined (Fig, 2). A control experiment was performed in which the magnitude of a 5-hydroxytryptamine induced contraction was measured . After washing the preparation, a mixture of 5-hydroxytryptamine and melatonin in varying molar ratios was added. Since the response to successive administrationof 5-hydroxytryptamine graduallydeclines, eachpreparationwas used only twice and then discarded. Every horizontal line in Fig, 2 represents a different preparation. These experiments show that melatonincauses a reductionintheresponseto5-hydrozytryptamine, Withanincreaseinthemelatonin : 5-hydroxytryptamine ratio the magnitude of contraction decreases, Ratio Melatonin 5HT
~0 !.i
nMlml SHI
l .inMlml SHI i
160 l.i nMlml SHI l,inMlml SHI+ lS6 nMiml MNalon~n
1
1,6 nMlml SHI
.l~lUVU
t l,inMlml
76 " nMlml
G80
SHI+ Melalon~n
6~0 l,i
nMlml SNI I6nMlml SHI+ !0?f nMlml M~lafon~n
FIG. 2 Effect of different concentrations of melatonin on 5-hydroxytryptamine induced contractions
Vol . 4, No . 14
EFFECT OF MELATONIN
1571
(3) Effect on Isometric Contractions Essentially the same results have been obtained when tones variatonns of uterine smooth muscle, in response to melatonin and serotonin, are recorded . Serotonin causes an increase in tones, while melatonin decreases the tones. Melatonin also abolishes the increased tones induced by serotonin. Discussion Our finding that melatonin causes an inhibition of the contractility of uterine smooth muscle is another instance of suppression of the activity of the female genital system by this substance . The mechanism of this action is still unknown.
In preliminary ex-
periments in which the spontaneous electrical activity of the uterine muscle was recorded with ezternal electrodes, a diminution of aplitude and fre quency resulted after application of melatonin .
The inhibitory effect of me-
latonin on uterine contractility might thus be explained by decreasing the excitability of this preparation. It should be noticed however that the amounts of melatonin used by other investigators and by us, .are probably greater than the supposed physiological concentration.
Since, neither the rate of pénetration of melatonin
into the muscle cells nor its site of action are known, it is difficult at the present time to postulate that variations in the melatonin level have an effect on sexual activity in the rat in viw.
In order to approach solution of these
problems, further experiments in vivo and in vitro are required . Summary Melatonin, a substance isolated from the pineal body, causes an inhibition of spontaneous and aerotonin-induced contractions of the oeatrogenized rat ute rua .
1372
Vol. 4, No. 14
EFFECT OF MELATONIN Acknowledgments
The authors wish to thank Prof. J. Magnea for his constructive advice in this work . They are indebted to Mr . S. Ben-Yonah for his aid in preparing the diagrams . References 1.
Lerner, A, B., J. D, Case, Y. Takahashi, T. H. Lee and W, Mori, J. Amer. Chem . Soc. $~,, 2587 (1958) .
2.
Azelrod, J. and H. Weissbach, Science, 1~, 1312 (1860) .
3 . Weissbach, H. , B. G. Redüeld and J. Azelrod, Biochim. Biophys . Actes, 4~, 352 (1960) . 4. Quastel, M. R . and R. Rahamimoff, Brit . J. Pharmacol. - in press (1965). (in preparation) .
5.
Rahamimoff, R .
6.
Chu, E. W., R. J. Wurtman and J. Axelrod, Endocrinol. 7~5 238 (1964) .
7.
Mclsaac, W, M. , R. G. Taboraky and G. Farrel, Science, 1= , 63 E1964) .
8.
Wurtman, R. J., J. Axelrod and E. W. Chu, Science, 141 , 277 (1963) .
9.
Kappera, J. A, , Abstracts, 16th Intern. Congr. Zool . Washington, D. C . 3, 238 (1963) .
10 .
Umbreit, W. W. , R . H. Burris and J. F. Stauffer (1957) .
Manometric
Techniques, p. 149, Minneapolis, Burgess Publishing Co .
Pergamon Press Ltd.
Printed in
EFFECT OF MELATONIN ON UTERINE CONTRACTILTTY* Margalit Hertz-Eshel** and R. Rahamimoff The Department of Physiology, Hebrew University Hadassah Medical School, Jerusalem, Israel
(Received 12 May 1965)
Since the isolation of melatonin (5 Methoxy-N-Acetylti~yptamine) from the pineal body in 1958 by Lerner at al . (1) and the discovery of its enzymatic synthesis from 5-hydroxytryptamine (serotonin) in the same organ {2, 3), there has been increasing interest in the function of this substance. Melatonin inhibits the spontaneous motility of isolated rat duodenum and abolishes the 5-hydroxytryptamine induced contractions of this preparation {4).
It has also been observed that melatonin decreases the exci-
tability of frog sciatic nerve in vitro (5). Furthermore, it has been shown that m~~latonin has a definite effeet on the female rat genital system, causing a decrease in the incidence of oestrus, following intraperitoneal or subcutaneous injection (6, 7) and
* Com-nunicated to the 5th Scientific Meeting of the Israel Physiological and Pharmacological Society . Nes-Ziona, 23rd February l~fi5 . ** Part of M. Sc . thesis . 1367
1388
EFFECT OF MELATONIN
interfering with growth and maturation of the ovary (8).
Vol. 4, No. 14 Melatonin also de-
creases the seminal vesicle weight in male rate (9). In view of the inhibitory effect of melatonin on excitable tissues and its action on the female genital system, we thought it desirable to study the effect of melatonin on the activity of uterine smooth muscle . Materiale and Methode Female rats of Sabre strain (80-100 grams) were treated for three days with a daily dose of 50 ~tg~100 gr body weight, diethylstilbestrol previou~ to the performance of the experiments in order to sensitize the uteri. The animals were sacrificed by stunning and cervical fracture and the uterine horns were dissected out. The uteri were mounted vertically in a bath containing Krebs-Ringer bicarbonate solution (10) at 37°C through which a gaseous mixture of 95°Jo oxygen and
5°Jo C02
was bubbled.
The contractions were recorded isotoni
cally on a Kymograph or isometrically with a force displacement transducer (FT03) on a polygraph (Grass 5P).
The preparation was allowed to equilib-
rate for 30 minutes before addition of serotonin (5-hydroxytryptamine creatinine Sulphate - Light and Co . Ltd . Colnbrook, England) or melatonin (Regis Chemical Co ., Chicago, IIl., U. S. A.) or a mixture of these two compounds . The results presented here are based on 78 experiments done on 40 rata .
Each uterus served as its own control since some variability in
amplitude and frequency of contractions was observed .
Vol. 4, No . 14
EFFECT OF MELATONII3
1369
Results (1) Inhibition of Spontaneous Contractions On addition of melatonin at a final concentration of ~0 X 10
-9
moles f
/ml to uteri contracting spontaneously, a slit inhibition of the contractions is observed . -9
160 X 10 X 10
-9
When the concentration of melatonin is increased to
moles f ml the inhibition increases. A concentration of 300 X
moles/ml completely inhibits the spontaneous contractions (Fig . 1) .
a. 160 nM/ml Mtlctonin
300
nM/ml
Melatonin
1 min
FIG. 1
Inhibition of spontaneous contractions rat uterus by melatonin
1370
EFFECT OF MELATONIN
Vol. 4, No . 14
(2) Inhibition of 5-hydrox~rtryp tamine Induced Contractions 5-hydroxytryptamine, which is one of the most potent contracting agents for uterine smooth muscle, is related chemically to melatonin. The mutual relationship of these two substances on the uterine motility has therefore been examined (Fig, 2). A control experiment was performed in which the magnitude of a 5-hydroxytryptamine induced contraction was measured . After washing the preparation, a mixture of 5-hydroxytryptamine and melatonin in varying molar ratios was added. Since the response to successive administrationof 5-hydroxytryptamine graduallydeclines, eachpreparationwas used only twice and then discarded. Every horizontal line in Fig, 2 represents a different preparation. These experiments show that melatonincauses a reductionintheresponseto5-hydrozytryptamine, Withanincreaseinthemelatonin : 5-hydroxytryptamine ratio the magnitude of contraction decreases, Ratio Melatonin 5HT
~0 !.i
nMlml SHI
l .inMlml SHI i
160 l.i nMlml SHI l,inMlml SHI+ lS6 nMiml MNalon~n
1
1,6 nMlml SHI
.l~lUVU
t l,inMlml
76 " nMlml
G80
SHI+ Melalon~n
6~0 l,i
nMlml SNI I6nMlml SHI+ !0?f nMlml M~lafon~n
FIG. 2 Effect of different concentrations of melatonin on 5-hydroxytryptamine induced contractions
Vol . 4, No . 14
EFFECT OF MELATONIN
1571
(3) Effect on Isometric Contractions Essentially the same results have been obtained when tones variatonns of uterine smooth muscle, in response to melatonin and serotonin, are recorded . Serotonin causes an increase in tones, while melatonin decreases the tones. Melatonin also abolishes the increased tones induced by serotonin. Discussion Our finding that melatonin causes an inhibition of the contractility of uterine smooth muscle is another instance of suppression of the activity of the female genital system by this substance . The mechanism of this action is still unknown.
In preliminary ex-
periments in which the spontaneous electrical activity of the uterine muscle was recorded with ezternal electrodes, a diminution of aplitude and fre quency resulted after application of melatonin .
The inhibitory effect of me-
latonin on uterine contractility might thus be explained by decreasing the excitability of this preparation. It should be noticed however that the amounts of melatonin used by other investigators and by us, .are probably greater than the supposed physiological concentration.
Since, neither the rate of pénetration of melatonin
into the muscle cells nor its site of action are known, it is difficult at the present time to postulate that variations in the melatonin level have an effect on sexual activity in the rat in viw.
In order to approach solution of these
problems, further experiments in vivo and in vitro are required . Summary Melatonin, a substance isolated from the pineal body, causes an inhibition of spontaneous and aerotonin-induced contractions of the oeatrogenized rat ute rua .
1372
Vol. 4, No. 14
EFFECT OF MELATONIN Acknowledgments
The authors wish to thank Prof. J. Magnea for his constructive advice in this work . They are indebted to Mr . S. Ben-Yonah for his aid in preparing the diagrams . References 1.
Lerner, A, B., J. D, Case, Y. Takahashi, T. H. Lee and W, Mori, J. Amer. Chem . Soc. $~,, 2587 (1958) .
2.
Azelrod, J. and H. Weissbach, Science, 1~, 1312 (1860) .
3 . Weissbach, H. , B. G. Redüeld and J. Azelrod, Biochim. Biophys . Actes, 4~, 352 (1960) . 4. Quastel, M. R . and R. Rahamimoff, Brit . J. Pharmacol. - in press (1965). (in preparation) .
5.
Rahamimoff, R .
6.
Chu, E. W., R. J. Wurtman and J. Axelrod, Endocrinol. 7~5 238 (1964) .
7.
Mclsaac, W, M. , R. G. Taboraky and G. Farrel, Science, 1= , 63 E1964) .
8.
Wurtman, R. J., J. Axelrod and E. W. Chu, Science, 141 , 277 (1963) .
9.
Kappera, J. A, , Abstracts, 16th Intern. Congr. Zool . Washington, D. C . 3, 238 (1963) .
10 .
Umbreit, W. W. , R . H. Burris and J. F. Stauffer (1957) .
Manometric
Techniques, p. 149, Minneapolis, Burgess Publishing Co .