Pineal 5-methoxy tryptophol in man

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: Discussionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 95%

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

109

“…As with the bovine enzyme (Morton, 1986), trout HIOMT was capable of methylating all the hydroxyindoles commonly found in the pineal gland (Table 1) which raises the possibility that methoxyindoles other than melatonin may be physiologically active particularly as these substances have been suggested to be bioactive (Mullen et al, 1979;Pevet, 1983;Reiter and Vaughan, 1977). Of particular interest was the observation that hydroxytryptophol had a similar affinity to the melatonin precursor, N-acetylserotonin, for trout HIOMT and it is possible, therefore, that methoxytryptophol may be physiologically important in the trout as a mediator of pineal activity.…”

Section: Discussionmentioning

confidence: 97%

Probable mechanism of catalysis of pineal gland hydroxyindole-O-methyltransferase (HIOMT) from rainbow trout (Salmo gairdneri)

Morton

Forbes²

1989

Activity of trout pineal HIOMT was found to increase with increase in incubation temperature from 5 to 40 degrees C although the activation energy remained constant over this range. From examination of the effects of the products of HIOMT catalysis on the enzyme it was apparent that the catalytic mechanism was ordered Bi-Bi with S-adenosylmethionine as the obligatory first substrate. Trout HIOMT was found to methylate all the common pineal hydroxyindoles with hydroxytryptophol having the greatest affinity for the enzyme. The pH optimum for trout HIOMT was found to be about pH 9.0 although routine use of a pH of 7.9 is recommended to limit potentially deliterious effects caused by degradation of S-adenosylmethionine at elevated pHs.

“…It is, however, also known that, like melatonin, 5-methoxytryptophol is capable of modifying sexual development and reproduction in birds and mammals (Balemans, 1972(Balemans, a, b, 1974Mclsaac et al, 1964;Mullen et al, 1979).…”

Section: Introductionmentioning

confidence: 97%

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

Pévet

Haldar-Misra

Öcal

1981

S.c. injection of 25 microgram of methoxytryptamine (5-MT) in oil into adult male hamsters given between 4.30 and 5 p.m. (light on from 5 a.m. to 7 p.m.: 14 L/10 D) for 51 consecutive days caused involution of the testes. Similar injections of 5-MT given between 8.30 and 9.30 a.m. completely failed to cause regression of the gonads. Under the same conditions, 5-methoxytryptophan (5-MTP) did not induce gonadal atrophy, neither in the morning nor in the late afternoon. These results indicate that, like malatonin, 5-methoxytryptamine is implicated in the control of the reproductive function.