The Influence of Some Pteridines on the Circadian and Seasonal Rhythmicity of Hydroxyindole-O-Methyltransferase (HIOMT) in the Pineal Gland of 42-days-old Male Wistar Rats

Ebels, I.; Balemans, M. G. M.; Benthem, Jan van; Moreé, A. de; Berlo, M. F. van; Legerstee, W. C.

doi:10.1016/b978-0-08-026400-4.50033-5

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“…These findings point to a seasonal influence of RN on the formation of various methylating compounds in the pineal gland. A seasonal rhythmicity regarding the influence of RN was already found by Ebels et aL (1980), who showed in rats that RN only influenced the synthesis of aMT/ML when the synthesis of these compounds is maximal at midnight. Balemans et al (1980) showed in rats also a shift in the synthesis of MI under the influence of pteridines, which seems to be comparable to data found during the study of the seasonal rhythmicity in the synthesis of the MI.…”

Section: Discussionmentioning

confidence: 82%

“…The influence of RN on the synthesis of MI may be due to a) the influence of RN on tryptophanhydroxylase, b) an influence on HIOMT-activity: Cremer- Bartels et al (1975), demonstrated that pteridines in a certain period of the year may stimulate HIOMT-activity, or c) a different influence of RN on the proposed isoenzymes of HIOMT. An effect of RN on the methylating capacity of the pineal was already demonstrated in rats by Balemans et al (1980 and Ebels et al (1980). Apart from shifts in the maxima of synthesis of different MI dependent of the season, an increased synthesis of MW and MT and a decreased aMT/ ML synthesis was found.…”

Section: Discussionmentioning

confidence: 82%

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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

Benthem

Ebels

Balemans

et al. 1985

J. Neural Transmission

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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.

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Section: Discussionmentioning

confidence: 82%

Section: Discussionmentioning

confidence: 82%