Estimation of the methylating capacity in the pineal gland of the rat with special reference to the methylation of N-acetylserotonin and 5-hydroxytryptophol separately

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109

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.

Section: Methodsmentioning

confidence: 99%

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

Pévet

Balemans

Legerstee

et al. 1980

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109

“…The method mentioned is a modification of a technique previously described (Balemans et aL, 1978 a, b).…”

Section: Methodsmentioning

confidence: 99%

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

Flight

Mans

Balemans

1983

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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.

“…The method to determine pineal methylating capacity, expressed as the synthesis of the various MI, has been reported elsewhere in detail (Balemans et al, 1978 a, b). The animals were killed by decapitation.…”

Section: Methodsmentioning

confidence: 99%

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

Benthem

Mans

Ebels

et al. 1985

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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.