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

Abstract

SummaryThe 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.

Melatonin biosynthesis in plants: multiple pathways catalyze tryptophan to melatonin in the cytoplasm or chloroplasts

“…The low level of melatonin synthesis through multiple biosynthetic pathways is consistent with the recent proposal that melatonin may function as a signal molecule in plant growth and development, as well as in the defense response against various adverse environments, including abiotic and biotic stresses . Other melatonin biosynthetic routes not mentioned in this review may exist, in which 5‐hydroxytryptophan is methylated by ASMT/COMT to 5‐methoxytryptophan, which is decarboxylated to 5‐methoxytryptamine by TDC followed by conversion to melatonin by SNAT . However, we found that neither ASMT nor COMT was capable of converting 5‐hydroxytryptophan into 5‐methoxytryptophan (K Back and K Lee, unpublished data).…”

“…4,14,[93][94][95][96] Other melatonin biosynthetic routes not mentioned in this review may exist, in which 5-hydroxytryptophan is methylated by ASMT/COMT to 5-methoxytryptophan, which is decarboxylated to 5-methoxytryptamine by TDC followed by conversion to melatonin by SNAT. 12,97 However, we found that neither ASMT nor COMT was capable of converting 5-hydroxytryptophan into 5-methoxytryptophan (K Back and K Lee, unpublished data). Similarly, rice TDC1 did not catalyze 5-methoxytryptophan into 5-methoxytryptamine (K Back and K Lee, unpublished data).…”

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

“…An increase in MW, MT and aMT synthesis is always coupled with a decrease in ML and MA. This fact was earlier demonstrated by Balemans et al (1983 b) in rats. Moreover, when a high production of aMT is requested, its putative precursors MT and MW show also an increased synthesis.…”

“…It can be methylated or metabolized into MT or HB which may also be important substances in the indole metabolism. Balemans et aL (1983 b) proposed an alternative way of synthesis ofaMT (Fig. 9 B).…”

In Vitro Uptake and Metabolism of [3H]Indole Compounds in the Pineal Organ of the Pike. I. A Radiochromatographic Study

“…Such a radiation and/or possibly some ['HIHT metabolites (which do not accumulate in such high amounts in natural conditions) might have affected the NAT activity or levels of compounds necessary to this activity (e.g., acetyl-coenzyme A, cyclic nucleotides) [see Klein et al, 1981;Trentini et al, 19821. 2)As it has been shown in organ culture of hamster pineals [Craft and Reiter, 19841, some still unknown factors, different from direct photosensitivity and which cannot be expressed in in vitro conditions, might be necessary to enhance the N-acetylation pathway. Although any comparison is difficult, interesting is the fact that the in vivo uptake of ['HIHW led to the production of more acetylated than deaminated products in the parakeet pineal organ [Collin et al, 19821 whereas the opposite is true after in vitro uptake of ['HIHT Uuillard et al, 19831. 3) As suggested by Balemans et al [1983], the synthetic pathway for aMT biosynthesis could be different from the one generally accepted. Such a pathway would involve a decarboxylation of MW followed by the N-acetylation of the neosynthetized MT.…”