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

5-Methoxytryptophan-dependent inhibition of oral squamous cell carcinoma metastasis

The metastatic status of oral cancer is highly associated with the overall survival rate of patients. Previous studies have revealed that the endogenous tryptophan metabolite 5-methoxytryptophan (5-MTP) can downregulate cyclooxygenase-2 expression; suppress tumor proliferation, migration, and invasion; and reduce the tumor size. To improve the understanding of the molecular mechanisms involved in the regulation of 5-MTP in the tumorigenesis of oral cancer, we conducted a comparative wound healing and transwell invasion assays. Our results revealed that 5-MTP reduce oral cancer cell migration and invasion ability. In addition, the results of an in vivo assay demonstrated that the growth of primary tumors was significantly inhibited by 5-MTP in OC3 oral cancer cells and in invasive OC3-I5 oral cancer cells. Moreover, enlarged spleens were observed in OC3-I5-implanted severe combined immunodeficiency mice although 5-MTP can inhibit spleen enlargement. Through comparative proteomics, we identified 32 differentially regulated protein spots by using 2D-DIGE/MALDI-TOF MS analyses. Some of the differentially regulated proteins such as amadillo-repeat-containing X-linked protein 1, phosphoglycerate kinase 1, tropomyosin alpha-1, and tropomyosin alpha-4 may be associated with the 5-MTP-dependent inhibition of oral cancer growth and metastasis. We conclude that 5-MTP plays a crucial role in inhibiting in vitro and in vivo cancer invasion and metastasis.

5-Methoxytryptophan-dependent protection of cardiomyocytes from heart ischemia reperfusion injury

5-Methoxytryptophan (5-MTP), a catabolic product of tryptophan, can block Cox-2 overexpression in cancer cells as well as suppress cancer cell growth, migration and invasion. The aim of this study was to in vitro examine whether 5-MTP is able to reduce reactive oxygen species (ROS)-induced heart ischemia reperfusion injury and activate the cardiomyocyte's damage surveillance systems. Accordingly, rattus cardiomyocytes were treated with H2O2 as a heart ischemia reperfusion model prior to incubation with/without 5-MTP and proteomic analysis was performed to investigate the physiologic protection of 5-MTP in H2O2-induced ischemia reperfusion in cardiomyocyte. Our data demonstrated that 5-MTP treatment does protect cardiomyocyte in the ROS-induced ischemia reperfusion model. 5-MTP has also been shown to significantly facilitate cell migration and wound healing via cytoskeletal regulations. Additionally, two-dimensional differential gel electrophoresis (2D-DIGE) combined matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF/TOF MS) analysis showed that 5-MTP might modulate growth-associated proteins, cytoskeleton regulation, redox regulation and protein folding to stimulate wound healing as well as prevent these ischemia reperfusion-damaged cardiomyocytes from cell death through maintaining cellular redox-balance and reducing ER-stress. To our knowledge, we report for the first time the cell repair mechanism of 5-MTP against ischemia reperfusion-damage in cardiomyocytes based on cell biology and proteomic analysis.

Effect of intra-testicular melatonin injection on testicular functions, local and general immunity of a tropical rodent Funambulus pennanti

Local antigonadotrophic action of melatonin in testes has never been correlated with local and general immune status of any rodent. Intra-testicular injection of melatonin (2.5 μg/50 μl) for 10 days (MI-10D) and 20 days (MI-20D) was given to young adult male of Funambulus pennanti and testicular androgen receptor (AR), androgen binding protein (ABP) expression, 3β-hydroxysteroid dehydrogenase (3β-HSD) activity, and Mel1aR expression in thymus was checked along with general immune parameters. Further, immunohistochemical localization of Mel1aR in testes was done. Decreased AR, ABP expression, testes weight, 3β-HSD activity, testosterone level, and spermatogenesis but increased Mel1aR expression in thymus, immunoreactivity in testes, and testicular macrophages following injection was noted. Lymphatic tissue weight, leukocyte, lymphocyte count, lymphocyte proliferation in spleen, thymus, plasma melatonin, and IL-2 level increased in a duration-dependent manner following intra-testicular injection. Intra-testicular injection of melatonin decreased steroidogenesis by enhancing the primary effect of melatonin on Leydig cell endocrine function. Along with reduced circulatory testosterone production, an increase in testicular as well as general immunity was observed in a duration-dependent manner. Therefore, a local participation of melatonin in testes of F. pennanti to control testicular androgen production is suggested.

Effect of pineal indoles on the chick embryo

In a study on the embryotoxicity of pineal indoles on developing chick embryos in vivo, the pineal indoles--namely, melatonin (MEL), methoxytryptamine (MTA) and methoxytryptophol (MTP)--were injected into the yolk sacs of the chick embryos through the air chambers of the eggs on the 4th day of incubation. The eggs were opened and the embryos examined after 6, 10 or 14/15 days of incubation. Abnormalities were found to occur mainly in the 6- and 10-day-old embryos, which exhibited external malformations such as twisted vertebral column, abdominal hernia, exteriorization of heart and viscera, defects of eye, beak and limb. From the results obtained from embryos on the 14th or 15th day of incubation, MEL was found to be the most toxic indole in regard to the mortality induced, whereas MTA had the highest teratogenicity because of the frequent incidence of abnormal embryos. Effect of MTP treatment on the development of chick embryos varied greatly between doses, and there were no abnormal embryos found on the 14th or 15th day of incubation.

Changes induced by pineal indoles in post-implantation mouse embryos

1. A subcutaneous injection of hydroxyindoleacetic acid (HIAA), melatonin (MEL), methoxytryptophol (MTP) or methoxytryptamine (MTA) (1 mg/25 g body wt/injection) at 8.5 days post-coitum (p.c.) did not produce any effect on the development of embryos in utero at 10.5 days p.c. 2. Two subcutaneous injections (3 mg/25 g body wt/injection) of MTP, but not HIAA, MEL nor MTP, at 7.5 and 8.5 days p.c. brought about a decrease in gravid uterine weight and number of live fetuses and an increased incidence of early resorptions at 17.5 days p.c. 3. MEL at doses 100 and 200 micrograms/ml, MTP at doses 50 and 100 micrograms/ml and MTA at 25, 50 and 100 micrograms/ ml brought about an increase in the number of abnormal embryos cultured in vitro and an increased incidence of abnormal yolk sac circulation, body axis, optic and otic placodes, branchial apparatus, forelimb buds and cranial neural tube. 4. The findings show than melatonin, methoxytryptamine and methoxytryptophol produced an embryotoxic effect on embryos at the early somite stage in vitro while only methoxytryptamine had an adverse effect on embryonic development in vivo.

Effect of photoperiod on testicular histology in golden hamsters and C57 and BALB/C mice

The effects of different photoperiods (14L:10D, 12L:12D, and 8L:16D) on testes and accessory sex organs were examined in mature male golden hamsters, C57 mice, and Balb/c mice. The seminiferous tubules of hamsters exposed to the 14L:10D and 12L:12D photoperiods contained various stages of spermatogenesis, while the testes of hamsters maintained under the 8L:16D photoperiod were atrophic. The seminal vesicles of hamsters kept under the 14L:10D and 12L:12D photoperiods possessed tall columnar epithelial cells and abundant secretion in the lumen. In contrast, the seminal vesicles of hamsters exposed to the 8L:16D photoperiod had an epithelium made up of low columnar or cuboidal cells and contained a reduced amount of secretion in the lumen. The histological appearances of testes and seminal vesicles of C57 and Balb/c mice exposed to the three different photoperiods were similar.

Development of pre-implantation mouse embryos under the influence of pineal indoles

The developmental toxicity of pineal hormones on mouse embryos was examined both in vitro and in vivo. Pregnant ICR mice were divided into groups which received at 1.5 days post-coitum (p.c.) and again at 2.5 days p.c. a subcutaneous injection of one of the following pineal indoles: hydroxyindoleacetic acid (HIAA), melatonin (MEL), methoxytryptophol (MTP) or methoxytryptamine (MTA). Mice treated with the injection vehicle served as the control. The animals were sacrificed at 17.5 days p.c. The pineal indole treatment did not cause changes in the gravid uterine weight, numbers of implants, early resorption, late resorption, dead fetuses and live fetuses, fetal weight or fetal crown-rump length, and did not produce embryos with external or visceral defects. However, some mice treated with MTP or MTA produced litters in which all embryos underwent resorption. Cultured embryos at the 4-cell stage were treated with the aforementioned pineal indoles and examined after 24, 48, 72 and 96 hours. It was found that MTA retarded embryonic development at all time points studied. HIAA also produced a slight inhibitory effect on embryonic development. Some embryos underwent degeneration in response to the MTA and HIAA treatments. However, MEL- and MTP-treated embryos were in general developmentally similar to control embryos. When cultured embryos were treated at the 8-cell to compacting stage, it was found that MTA exerted only a slight retarding effect on embryonic development, while other indoles were devoid of any conspicuous effects.

The significance of the metabolism of the neurohormone melatonin: antioxidative protection and formation of bioactive substances

Recent findings suggest that the ability of melatonin to enter all body tissues and to be metabolized, enzymatically or nonenzymatically, in any of them results in a spectrum of effects, which exceed substantially those transduced by membrane receptors. These actions comprise the formation of various bioactive compounds such as N-acetylserotonin, 5-methoxytryptamine, N,N-dimethyl-5-methoxytryptamine, 5-methoxytryptophol, cyclic 2-hydroxymelatonin, pinoline, and 5-methoxylated kynuramines. Apart from enzymatic metabolism, nonenzymatic reactions with free radicals, in particular the superoxide anion and the hydroxyl radical, represent a new and significant aspect of melatonin's biological role. Melatonin represents the most potent physiological scavenger of hydroxyl radicals found to date, and recent findings suggest an essential role of this indoleamine for protection from hydroxyl radical-induced carcinogenesis and neurodegeneration.

Action of pineal indoleamines on the reproductive systems of the male C57 mouse and golden hamster

Intraperitoneal administration of melatonin, methoxytryptamine and methoxytryptophol in the late afternoon to mice exposed to a 14L:10D photoperiod induced appearance of necrotic cells in seminiferious tubules and an increase in incidence of aspermic tubules. The histological appearances of the seminal vesicles and coagulating glands were, however, unaffected by the treatments. Treatment of mice with methoxyindoleacetic acid did not produce discernible changes in the testes and accessory sex organs. Subcutaneous injections of the aforementioned pineal indoles at a dose of 250 micrograms/injection for 3 months to mature male hamsters kept under a 14L:10D photoperiod did not evoke changes in the testes, seminal vesicles and coagulating glands, suggesting a down-regulation of melatonin receptors by administration of a high dose of pineal indole over a prolonged period.

Inhibitory influence of late afternoon melatonin injections and the counter-inhibitory action of melatonin-containing pellets on thyroid growth process in male Wistar rats: comparison with effects of other indole substances

Previous studies performed in our laboratory indicated that melatonin, when administered in late afternoon (1600-1800) as s.c. injections for 10 days, exerted an inhibitory effect on thyroid growth in mice and Sprague-Dawley rats. The goal of the present study was to examine the effects of melatonin and other indole substances (5-methoxytryptophol, N-acetylserotonin, 6-methoxytryptamine), administered for 10 days, for either 4, 8, or 10 weeks, on thyroid growth processes in adult male Wistar rats. We have also compared the action of melatonin administered in late afternoon as s.c. injections with effects of the melatonin-released chronically from s.c. implanted beeswax pellets containing 1 mg of the hormone. Additionally, the effects of melatonin injections in animals with the pineal gland removed and in thyroid stimulating hormone (TSH)-injected rats have been studied. We examined the mean mitotic activity rates (MMARs) of thyroid follicular cells (TFC) and the wet thyroid weights. We concluded that melatonin, of the examined substances, is the most potent inhibitor of thyroid growth; the hormone reduced the MMAR of TFC and the thyroid weight at all time-points. 5-Methoxytryptophol, like melatonin, exerted the inhibitory influence on the mitotic activity; however, it did not affect thyroid weight. The influence of other indole substances was much less pronounced. It was shown that melatonin-pellets prevented the inhibitory effect of late afternoon melatonin injections on thyroid growth processes. This observation is consistent with results of other authors concerning the counter-antithyroid effect of melatonin on thyroid hormone secretion. Pinealectomy revealed the stimulatory effect on thyroid growth processes, while melatonin treatment reversed the effect of the surgery.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of different photoperiods on the diurnal rhythm of 5-methoxytryptamine in the pineal gland of golden hamsters (Mesocricetus auratus)

This study tested the photo-dependency of the rhythmic synthesis of 5-methoxytryptamine (5-MT) in the pineal gland of golden hamsters. After pargyline administration, pineal 5-methoxytryptamine and melatonin were measured by HPLC in male golden hamsters kept under short and long photoperiod. In both photoperiodic regimes, a clear 5-MT rhythm was observed which fitted a sinusoidal function with high values occurring during the daytime and low values occurring during the night-time. The duration of the low night-time levels was clearly proportional to the length of the dark phase. A marked rhythm of melatonin synthesis was also seen with low daytime levels and high night-time values. An inverse relationship between 5-MT and melatonin levels was observed. Thus, after pargyline administration, the rhythms of 5-MT and melatonin in the pineal gland of golden hamsters are photoperiod-dependent and show a reciprocal relationship.

Low ambient temperature does not affect the pineal concentrations of either 5-methoxytryptamine or melatonin in golden hamsters kept under short photoperiod

This work investigates the rhythmic synthesis of pineal 5-methoxytryptamine and related indoles in golden hamsters as a function of ambient temperature. 5-methoxytryptamine, 5-methoxytryptophol, 5-methoxyindole acetic acid, and melatonin were measured by high pressure liquid chromatography (HPLC) in the pineal gland of golden hamsters after inhibition of monoamine oxidase. In our experimental conditions, the pineal 5-methoxyindole concentrations of hamsters kept at 5 degrees C were similar to those observed at 20 degrees C. These results suggest that low temperature, which is known to accelerate the short photoperiod-induced gonadal regression, acts at a level different to that of the pineal gland or affects another compound in the pineal gland.

Effect of pineal indoles on testicular histology of mice

The effect of late afternoon injections of melatonin, 5-methoxytryptamine, 5-methoxytryptophol, and 5-methoxyindole-3-acetic acid on testicular histology in mice were examined. Melatonin and 5-methoxytryptophol injections caused a reduction in the diameters of seminiferous tubules. The tests of melatonin-treated animals underwent some detectable regressive changes in the seminiferous tubules, whereas administration of 5-methoxytryptamine or 5-methoxytryptophol appeared to cause atrophy in some tubules. The percentage of aspermic tubules in melatonin-treated and methoxytryptamine-treated mice was significantly higher than that of the control. In involuted testes, some seminiferous tubules contained only Sertoli cells together with spermatogonia and spermatocytes, but no discernible spermatids and spermatozoa. Regressing spermatids and cell debris were frequently observed in the tubules. The tested of mice that received daily injections of 5-hydroxytryptophol and 5-methoxyindole-3-acetic acid were indistinguishable from those of the controls.

Histological studies on the effects of pineal 5-methoxyindoles on the reproductive organs of the male golden hamster

The effects of late-afternoon injections of melatonin (MEL), 5-methoxytryptamine (MTN), 5-methoxytryptophol (MTOL), and 5-methoxyindole-3-acetic acid (MIAA) on testicular and seminal vesicular histology in the golden hamster were examined. MEL, MTN, and MTOL injections caused a reduction in the diameters of seminiferous tubules and an inhibition of spermatogenesis. Testicular regression ranged from a decrease in the abundance of late spermatids and mature spermatozoa in some animals to an almost complete loss of spermatogenesis in others. Sertoli cells were more resistant to the treatment than other cellular components of the seminiferous tubules. Leydig cells were reduced in size, showed a great reduction in cytoplasm, and possessed shrunken and angular nuclei. The epithelial cells of seminal vesicles were reduced in size and became cuboidal or low columnar. Some secretory cells possessed pyknotic nuclei and had minimal secretory activity. MTN and MTOL appeared to be more potent than MEL in inducing the aforementioned changes, whereas MIAA failed to exert similar effects.

Effect of melatonin and 5-methoxytryptamine on sex steroids and thyroid hormones during the prespawning phase of the annual reproductive cycle in the freshwater teleost, Clarias batrachus

Melatonin and 5-methoxytryptamine have been studied in the freshwater teleost Clarias batrachus during the prespawning period. The data have provided evidence of the inhibitory effects on sex steroids and thyroid hormones when the pineal indoleamines melatonin and 5-methoxytryptamine (5-MT) are administered intramuscularly daily in the afternoon for 27 days. The different dose levels had different effects. The higher dose levels of melatonin showed the initiation of counter inhibitory impacts on testosterone and T3, T4 levels. The melatonin acted more effectively than 5-MT.

The effect of different photoperiods on the methylating capacity of the pineal gland of adult, male golden hamsters, with special reference to 5-methoxyindoles

Testes weight, plasma FSH and LH concentration and pineal methylating capacity were compared in hamsters housed under either long (LD14:10) or short (LD8:16) photoperiods. Hamsters housed for 14 weeks under short photoperiod showed gonadal atrophy, which was complete after 6 weeks. Also plasma FSH and LH concentration showed a marked decline after transfer to short photoperiod. However, after 14 weeks the concentration of FSH and LH as well as testes weight increased again. Under both photoperiods day/night rhythms in plasma FSH and LH concentration were measured. Under both light regimes the concentrations did not show significant differences. Under long as well as short photoperiods in the pineal gland of animals no significant differences were found in the daily synthesis of various MI tested. Only the synthesis of ML was significantly higher in the pineal of hamsters housed under short photoperiod. The function of this higher synthesis of ML remains unknown. Although the maxima of the rhythm for the various MI found under different LD regimes did not differ in magnitude or duration, their location in respect to the onset of darkness was different. It is suggested that this specific location is of more physiological importance than the quantity or duration of synthesis, concentration or release of MI. At the moment the day/night rhythms were determined there were indications that recrudescence of the testes had already started. It is suggested that this recrudescence is responsible for the fact that no differences in the synthesis of MI were found comparing the influence of both photoperiods. After 14 weeks of exposure to short photoperiod, aML synthesis was, in contrast to the synthesis of the other MI, (not significantly) higher under LD8:16. Moreover, opposite results for aMT and aML synthesis during darkness were found. It is suggested that the ratio of synthesis of these compounds is of physiological significance.

Daily and seasonal rhythmicity in the methylation of pineal indolic compounds in adult male golden hamsters, kept under natural conditions

Seasonal rhythmicity in the reproductive cycle was demonstrated in golden hamsters exposed to natural conditions. Testes regress in weight and function from October up to April. Reproductive functional testes are found in June. Although less marked, body weight also shows seasonal variations: a retarded growth in winter and early spring. In the pineal gland of these animals diurnal and seasonal rhythmicity was found in the synthesis of various MI. It has been concluded that rhythms in the pineal of animals kept under artificial conditions are often more pronounced as compared to those in hamsters kept under natural conditions. Melatonin (aMT) synthesis was observed during the day as well as during the night. A certain resemblance in patterns of day/night rhythms as to aMT and 5-methoxytryptamine (MT) production was reported suggesting a physiological role of MT. To facilitate the discussion on seasonal rhythmicity the average synthesis per day of the 5-methoxyindoles (MI) was calculated. During the period of gonadal regression in fall and early winter, MT and aMT, which are both generally accepted as pineal antigonadotropins, showed opposite patterns in rhythms of mean synthesis; MT decreased but aMT increased from October up to December. It was suggested that under natural conditions MT may induce and aMT maintain gonadal atrophy. Furthermore, also other MI showed relatively high amounts of production, at least in November. The period of recrudescence was characterized by a high synthesis of 5-methoxytryptophan (MW), 5-methoxytryptophol (ML) and O-acetyl-5-methoxytryptophol (aML). This confirms an earlier suggestion that aML can be considered a counter-antigonadotropic substance of the hamster pineal gland. Therefore it was concluded that, apart from MT and aMT, also other MI may be of physiological importance in the regulation of gonadal atrophy.

Rhythmic synthesis of various 5-methoxyindoles in the pineal gland of male adult golden hamsters, kept under the same artificial conditions throughout the year

Until now the day/night and seasonal rhythmicity in the synthesis of 5-methoxyindoles (MI) is thought to be regulated by environmental factors, especially photoperiod and temperature. Endogenous factors are also implicated in the generation of N-acetyltransferase and hydroxyindole-O-methyltransferase activity rhythms. In the present experiments seasonal rhythmicity in the synthesis of MI in the pineal gland was investigated in hamsters kept under the same artificial conditions throughout the year. Though the environmental conditions were the same, day/night and seasonal rhythmicity in the production of MI in the pineal were observed indicating the existence of endogenous factors influencing the rhythmicities. In November, most of the MI showed the highest synthesis, MA and ML excepted, which were especially produced in July and September. The results obtained sustain the hypothesis that aMT is synthesized from MT rather than from aHT. Moreover, the rhythmicities in aMT synthesis are not identical to those found in aMT concentration as described in the literature. This indicates that synthesis and concentration of a compound are not comparable. At the end of the light period, when aMT injections have an antigonadotropic effect, a peak of aMT synthesis was always present. Although MI synthesis showed seasonal rhythmicity, no reproductive cycle occurred in the hamsters. At present, the concept that the pro- and/or antigonadal effects of the pineal are mediated by aMT seems to be the most acceptable. The present results, however, indicate that aMT and perhaps other MI, often regarded as factors influencing gonadal growth in golden hamsters, are not the only factors involved.

Identification and quantification of 5-methoxyindole-3-acetic acid in human urine

A putative pineal metabolite, 5-methoxyindole-3-acetic acid, was quantified in human urine by a gas chromatographic-mass spectrometric method. Excretion of 4.77 +/- 2.25 microgram/day (mean +/- SD) was consistent from each of three normal subjects over 2-4 weeks. Excretion did not vary with regard to menstrual cycle. The daily pattern of excretion bore no relationship to that of 6-hydroxymelatonin, the major metabolite of melatonin, indicating that the major portion of urinary 5-methoxyindole-3-acetic acid does not derive from melatonin.

The effect of reduced neopterin on the synthesis of several methylated indoles in the pineal gland of adult male golden hamsters, kept under standardized conditions

In the present study the effect was tested of reduced neopterin (RN) on the methylating capacity of the pineal gland of adult, male golden hamsters, housed under standardized conditions throughout the year. An effect of RN on the synthesis of a number of methylated compounds was, indeed, demonstrated. It is concluded that RN not only influences the indole metabolism by being the cofactor of tryptophan-hydroxylase, but that it might be involved in the regulation of other enzymes as well. Incubation with RN was most effective at the end of the light period. As this is also the time at which melatonin (aMT) injections cause gonadal atrophy in hamsters, kept under long photoperiod, this time of the day may be very important for aMT synthesis. A season-bound influence of RN was also demonstrated. The effect of RN was stimulatory in September, November and January for 5-methoxy-tryptamine (MT) and in November for 5-methoxytryptophan (MW) synthesis, but inhibitory in July. Furthermore, the effect of RN was stimulating for 5-methoxyindole-3-acetic acid (MA) and aMT in September, while the influence in the other months tested was absent or slightly inhibiting. These results suggest that the influence of RN in the pineal may be regulatory to various enzymes of the indole metabolism.

Relative efficacy of melatonin and 5-methoxytryptamine in terms of their antigonadotrophic and counterantigonadotrophic actions in male Syrian hamsters

Antigonadotrophic and counterantigonadotrophic activities of melatonin and 5-methoxytryptamine (5-MT) were quantitatively compared in male Syrian hamsters. In long day conditions, the daily afternoon administration of either 5, 15, 25, 50, 100 or 200 micrograms melatonin induced testicular regression within 10 wk; under the same circumstances, only the 200-microgram dosage of 5-MT was able to suppress testicular weights. Thus, 5-MT appears to have about one-tenth the antigonadotrophic action of melatonin in the male Syrian hamster. In short days, the subcutaneous implantation of either 50 or 100 micrograms melatonin (every 2 wk in beeswax) prevented testicular regression whereas it required much larger doses of 5-MT (1 mg every 2 wk in beeswax) to achieve the same counterantigonadotrophic action. In terms of both their antigonadotrophic and counterantigonadotrophic effects, hamsters seem to be more sensitive to melatonin than to 5-MT.

Methoxyindole synthesis in the retina of the frog (Rana esculenta) during a diurnal period

In the present study, the synthesis of methoxyindoles in the neural part and in the pigment epithelial layer of the retina of the frog eye was investigated on the basis of naturally occurring substrate at regular intervals during a 24 hour period. Melatonin, 5-methoxytryptophol and 5-methoxyindole acetic acid were synthesized by the neural part of the retina only, while 5-methoxytryptamine and 5-methoxytryptophan were produced by both, the neural part of the retina and the pigment epithelium. The synthesis of melatonin and of 5-methoxytryptamine showed a diurnal rhythmicity. The results obtained clearly indicate that another cell type, i.e. pigment cells, is involved in indole metabolism besides photoreceptor elements. A possible functional relationship between different methoxyindoles and different retino-motor processes in the amphibian eye is discussed.

Day/night rhythmicity in the methylating capacities for different 5-hydroxyindoles in the pineal, the retina and the Harderian gland of the golden hamster (Mesocricetus auratus) during the annual seasons

In the pineal, the Harderian gland and the retina of the golden hamster the day/night capacity for the synthesis of different methoxyindoles is investigated under natural conditions for one 24-hour period in the months of December, March and June. The amounts of the methoxyindoles and the diurnal rhythms in the synthesis are different in the various months during which the tests were performed. There is a striking increase in the synthesis of melatonin and methoxytryptophol in all three organs in June as compared with December. Equally striking is the high synthesis of methoxytryptamine in the pineal in June, whereas this compound was not formed in the Harderian gland and the retina in this month. Methoxytryptophan synthesis was not observed in June in any of the three organs. Methoxyindoleacetic acid rhythmicity shows a pattern more or less identical to that of melatonin and methoxytryptophol. A high synthesis exists at the end of the June day, but greater fluctuations during the days of the two other months. Acetylmethoxytryptophol is synthesized in the pineal during the night in March, but in the late afternoon in June. The largest quantity of this compound is found in the Harderian gland in December, in the pineal in March and in the retina in June. The largest amounts of melatonin and methoxytryptophol are synthesized when gonadal weight is largest. The possible correlation between the amounts synthesized, the rhythmicities in synthesis and the reproductive system is discussed.

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.

Ability of tryptophan derivatives to mimic melatonin's action upon the Syrian hamster reproductive system

The ability of 18 different tryptophan derivatives to induce gonadal regression in Syrian hamsters when injected daily at either midday or late evening has been examined. The compounds chosen have either been identified within mammalian pineal glands or are thought to be possible metabolic derivatives of melatonin. Of the compounds tested, only melatonin and 5-methoxytryptamine were found to possess antigonadotropic activity. 5-Methoxy-tryptamine's potency, however, was 1/10th that of melatonin and, like melatonin, 5-methoxytryptamine was effective when injected in the evening but not when injected during midday. In addition to the general survey of tryptophan derivatives for antigonadal capability when injected, 5-methoxytryptamine, melatonin, and 5-methoxytryptophol were compared relative to their abilities to prevent photo-induced gonadal regression when administered within beeswax implants. Again 5-methoxytryptamine and melatonin, but not 5-methoxytryptophol, were effective with 5-methoxytryptamine's potency being less than that of melatonin. These results indirectly support the contention that melatonin is the pineal product which mediates photoperiodic effects upon the Syrian hamster reproductive system.

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 photoperiod and pineal indoles on the reproductive system of young female white-footed mice

Exposure of prepubertal female mice to short photoperiod (LD 8:16) for 3 weeks resulted in a significant inhibition of reproductive tract growth compared with mice maintained in long photoperiod (LD 16:8). Chronic subcutaneous melatonin-beeswax implants containing 1 mg melatonin also produced an inhibition of the reproductive system of these animals. The repressive effects of melatonin appear not to be influenced by photoperiod since comparable results were obtained from groups of mice bearing implants in long and short photoperiods. In addition, the ability of beeswax implants containing various indolic compounds (melatonin, serotonin, 5-methoxytryptamine, 5-methoxyindole-3-acetic acid, and N-acetylserotonin) to inhibit the growth of the reproductive system of this species were compared. Only implants containing melatonin or serotonin caused any significant repression of uterine and ovarian weights.

The independency of an intact pineal gland of the inhibition by 5-methoxytryptamine of the reproductive organs in the male hamster

Subcutaneous injections fo 25 micrograms of 5-methoxytryptamine (5-MT) in oil into intact and pinealectomized male hamsters given between 4.30 p.m. and 5 p.m. (light on from 5 a.m. to 7 p.m.; 14 L/10 D) for 54 consecutive days caused involution of the testes. 5-MT, however, is more effective when the pineal is present. These results indicate that melatonin is not the only pineal factor inducing gonadal atrophy in the hamster. 5-MT seems even more effective than melatonin in so far as it is, contrary to melatonin under the same experimental conditions, also effective in the absence of the pineal. Like melatonin, 5-MT appears to be implicated in the control of the reproductive function.