The inhibitory effect of 5-methoxytryptophol on ovarian weight, follicular growth and egg production of adult white leghorn hens (Gallus domesticus L.)

Physiological and pharmacological properties of 5-methoxytryptophol

5-methoxytryptophol (5-ML) is a pineal indoleamine derived from serotonin shown to be biologically active in a number of species. This indolamine exhibits a circadian pattern synchronized with the day-night cycle with significant increases during daylight, already recognized in vertebrates. The multiplicity of physiological and endocrine functions of 5-ML is remarkable; it is involved in circadian rhythms, reproduction and sexual processes. Furthermore, a number of pharmacological benefits of 5-ML have been reported, including immunomodulatory, antitumor and antioxidative activities. However, the molecular mechanisms of these pharmacological effects remain unclear. The purpose of this article is to provide an overview on the general properties and physiological functions of 5-ML. An attempt has been made to fully document all studies performed using 5-ML. In addition, this article aims to gain insight into the current state of knowledge regarding pharmacological and therapeutic effects of this indoleamine.

Seasonal effects of administration of melatonin and 5-methoxytryptophol on ovarian activity in the catfish Heteropneustes fossilis (Bloch)

In Heteropneustes fossilis, effects of intraperitoneal administration (25 micrograms/fish, alternate days for a month 1 hr before the onset of dark phase) of melatonin (MEL) and 5-methoxytryptophol (5-MTL) on ovarian activity were investigated during different seasons of the annual reproductive cycle under natural photothermal conditions. The gonadosomatic index (GSI) had decreased significantly by MEL during preparatory and prespawning seasons, and by 5-MTL in all but the spawning season. Both MEL and 5-MTL administrations arrested vitellogenesis during the gonadal recrudescence phase. As a result, stage I previtellogenic oocytes showed a significant increase in the MEL group in the preparatory and prespawning seasons, and in the 5-MTL group only in the prespawning season. Almost the same trend was noticed in the percentage distribution of stage 2 and 3 oocytes. The percentage distribution of stage 4 postvitellogenic oocytes decreased significantly during the preparatory and prespawning seasons, but not in the spawning season. The indole treatment resulted in a highly significant increase in the percentage distribution of atretic oocytes during prespawning, spawning, and post-spawning phases. Total protein content of the ovary was significantly lower in all seasons after MEL treatment, and only in the preparatory and prespawning seasons following 5-MTL treatment. The ovarian glycogen level was significantly lower in the preparatory and prespawning seasons (MEL group), and in the 5-MTL group only in the prespawning phase. Ascorbic acid level was inhibited by the indole treatment in all seasons except in the 5-MTL group during the post-spawning season. The results show that both MEL and 5-MTL are effective in inhibiting ovarian vitellogenesis and inducing atresia in the catfish.

The influence of some pteridines on pineal 5-methoxyindole synthesis in male Wistar rats periodically exposed to either white or green light

The pineals of 28 days old male Wistar rats, in December periodically exposed to either white or green light, were incubated with pterin-6-aldehyde or reduced neopterin. In white light the rhythm of synthesis of 5-methoxytryptophan and of 5-methoxyindole-3-acetic acid was clearly influenced by the pteridines mentioned. In green light a change in rhythmicity of 5-methoxytryptophan, 5-methoxytryptamine and of melatonin/5-methoxytryptophol synthesis by the pteridines was observed. In white light both pteridines increased 5-methoxytryptophan and decreased 5-methoxyindole-3-acetic acid synthesis. Reduced neopterin stimulated 5-methoxytryptamine synthesis and inhibited melatonin/5-methoxytryptophol synthesis. Pterin-6-aldehyde showed an opposite effect. In green light both pteridines decreased 5-methoxytryptophan synthesis, but increased 5-methoxyindole-3-acetic acid and 5-methoxytryptamine synthesis. Melatonin/5-methoxytryptophol synthesis was decreased by reduced neopterin and increased by pterin-6-aldehyde. The results suggest an indolic metabolic pathway leading from 5-methoxytryptophan via 5-methoxytryptamine to melatonin, while pteridines and light of different wave lengths are correlated in regulating indole metabolism.

Influence of some pteridines on pineal 5-methoxyindole synthesis in male Wistar rats periodically exposed to either white or red light

In previous investigations the change of circadian rhythmicity in pineal melatonin/5-methoxytryptophol synthesis of rats periodically exposed to red light was similar to that in pineals of rats incubated with pterin-6-aldehyde. These experiments were, however, performed with rats of different age and in different periods of the year. In the present study these two factors influencing pineal indole metabolism have been combined the experiments being carried out in rats aged 28 days and during the same day in the month of January. It was observed that under influence of red light the peak of melatonin/5-methoxytryptophol synthesis shifted towards daytime, whereas incubation with pterin-6-aldehyde did not cause such a shift. If under different experimental conditions the mean amount of melatonin/5-methoxytryptophol which was formed over a 24 hour period was compared, it appeared that pineals of rats exposed to white light incubated with reduced neopterin but not pineals incubated with pterin-6-aldehyde behave in this respect similar to pineals of rats exposed to red light. However, if the ratio between melatonin/5-methoxytryptophol and 5-methoxytryptamine is calculated pineals of white light exposed rats incubated in pterin-6-aldehyde behaved very similar to the pineals of rats exposed to red light. Although the role of pteridines remains obscure, it appears that the parameters 2. circadian rhythmicity and 2. the amount of 5-methoxyindoles and 3. the ratio between these indole derivatives might be of importance in analyzing their physiological effects. The influence of application of light of different wavelengths and year rhythmicity is discussed.

The effect of melatonin and other indole derivatives in maintaining ovulation in rats kept in continuous light and the influence of these indoles on HIOMT activity in the pineal gland

The aim of the present study was to investigate whether the ovulation-maintaining effect of melatonin in rats, exposed to continuous light (LL), was also exerted by other pineal indoles which have been reported to influence the reproductive processes of mammals. The effect of 10 micrograms melatonin was compared with that of similar amounts of either N-acetylserotonin, 5-methoxytryptophol, 5-methoxyindole-3-acetic acid, 5-hydroxytryptophol, 5-methoxytryptamine or 5-methoxytryptophan. All these compounds appeared to be significantly less effective than melatonin in preventing the effect of LL, ovulation being preserved in only 20--33% of the rats investigated, with melatonin this percentage being 60--75%. Investigations were also carried out to assess the effect of these indole derivatives on HIOMT (hydroxyindole-O-methyl transferase) activity in synthesizing different 5-methoxyindoles in the abnormally influenced pineal gland due to LL. Melatonin, the compound the effect of which on ovarian cyclicity is strongest, stimulates 5-methoxytryptophol synthesis; while other less active compounds stimulate the synthesis of melatonin and inhibit that of O-acetyl-5-methoxytryptophol. The possibility that the effect of other indoles than melatonin on ovarian cyclicity might be due to stimulation of melatonin synthesis was considered. A possible functional relationship of the different indoles cannot be excluded.

Effect of 5-methoxytryptophan and 5-methoxytryptamine on the reproductive system of the male golden hamster

S.c. injection of 25 microgram of methoxytryptamine (5-MT) in oil into adult male hamsters given between 4.30 and 5 p.m. (light on from 5 a.m. to 7 p.m.: 14 L/10 D) for 51 consecutive days caused involution of the testes. Similar injections of 5-MT given between 8.30 and 9.30 a.m. completely failed to cause regression of the gonads. Under the same conditions, 5-methoxytryptophan (5-MTP) did not induce gonadal atrophy, neither in the morning nor in the late afternoon. These results indicate that, like malatonin, 5-methoxytryptamine is implicated in the control of the reproductive function.

Circadian rhythmicity of the activity of hydroxyindole-O-methyl transferase (HIOMT) in the formation of melatonin and 5-methoxytryptophol in the pineal, retina, and harderian gland of the golden hamster

The day and night rhythms in the activity of HIOMT in the formation of melatonin of 5-methoxytryptophol have been determined in the pineal, retina and Harderian gland of the adult male golden hamster. In all hamsters used there was no detectable HIOMT activity in the deep pineal. In the superficial pineal HIOMT activity, involved in the synthesis of melatonin (Mel), was observed to be high at the end of the dark period and at the middle of the light period. Considering the HIOMT activity involved in the production of 5-methoxytryptophol (5-MTL), an increase in 5-MTL synthesis was observed only during the light period. Comparing the peak of Mel-production with that of 5-MTL it appears that during the light period the pineal produces more 5-MTL than Mel. In the Harderian glands, the circadian course of HIOMT activity involved in the synthesis of Mel seems to run parallel to that of the enzyme implicated in 5-MTL synthesis, both being stimulated at the end of the dark period. The activity of HIOMT in 5-MTL production is, however, always approximately 2 times higher than for Mel synthesis. In the retina the synthesis of Mel and 5-MTL is not significantly higher during the dark period than during the light period. However, the production of 5-MTL is larger than that of Mel. It appears that (1) with the exception of the end of the dark period, the extra-pineal synthesis of Mel and 5-MTL is always higher than that in the pineal; (2) the carcadian synthesis of 5-methoxyindoles is different in each organ, and (3) in the pineal the carcadian activity of HIOMT involved in 5-MTL formation is different from that of the same enzyme involved in the formation of Mel. The results are discussed.

Identification of O-acetyl-5-methoxytryptophenol in the pineal gland by gas chromatography-mass spectrometry

The presence of O-acetyl-5-methoxytryptophol in the pineal glands of rats kept in the dark for 8 h, but not in the light, has been shown by means of g.l.c.-mass spectrometry. It is suggested that this compound may be the biologically active precursor of circulating methoxytryptophol.

Separation of pineal extracts by gelfiltration. IV. Isolation, location and identification from sheep pineals of three indoles, identical with 5-hydroxytryptophol, 5-methoxytryptophol and melatonin

Aqueous extracts of sheep pineal bodies were separated on Sephadex G-25. A low molecular Sephadex G-25 fraction F4 was filtrated on Sephadex G-10. Several distinct peaks could be detected showing excitation and fluorescence maxima resembling those of indoles. A thinlayer chromatography study revealed that one Sephadex G-10 peak contained a spot identical with that of synthetic 5-methoxytryptophol, another a spot with the same Rf-values in different solvents as synthetic 5-hydroxytryptophol, while from a third peak a substance was isolated identical with synthetic melatonin. Mass spectra of the isolated compounds were recorded. These results are compared with those of previous isolation studies.