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

Abstract

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.

A Novel Protective Function of 5-Methoxytryptophan in Vascular Injury

“…On the other hand, organisms also exhibit intrinsic defense mechanisms to protect cells and tissues against pathophysiological stress and/or to repair damage. Tryptophan metabolites are involved in diverse physiological functions, including regulating circadian rhythms and reproduction 12 39 . In contrast to investigations in the immune and nervous systems of tryptophan metabolites 40 41 , study of tryptophan metabolism in vascular disease has been limited 42 43 44 45 .…”

“…5-Methoxytryptophan (5-MTP) is a 5-methoxyindole metabolite of tryptophan metabolism 9 10 . 5-Methoxyindoles such as melatonin, 5-methoxytryptamine, and 5-methoxytryptophol participate in the control of circadian rhythm in the pineal gland and retina 11 12 13 14 15 and are regarded as neuromodulators 16 17 . However, unlike these 5-methoxyindoles, the physiological function of 5-MTP is unclear, although it has been implicated a role in the pineal gland and retina 11 18 .…”

Polymorphic Cytochrome P450 2D6: Humanized Mouse Model and Endogenous Substrates

“…5-MT is believed to be formed by the deacetylation of MEL by arylacylamidase Rogawski et al, 1979), but may also be formed by the methylation of serotonin (5-HT) by hydroxyindole O-methyltransferase (Balemans et al, 1980). 5-Methoxytryptamine has been found in rat raphe nuclei, rat, golden hamster, sheep and human pineal, and hamster plasma (Beck and Bosin, 1979;Beck et al, , 1982Raynaud and Pevet, 1991a;van Benthem et al, 1985). 5-Methoxytryptamine has very poor affinity for MEL receptors (Sugden et al, 1997;Zawilska and Nowak, 1996).…”