Separation of pineal extracts by gelfiltration. IV. Isolation, location and identification from sheep pineals of three indoles, identical with 5-hydroxytryptophol, 5-methoxytryptophol and melatonin

Daily and light-at-night induced variations of circulating 5-methoxytryptophol (5-ML) in ewes with respectively high and low nocturnal melatonin secretion

The aim of the present study was to determine whether the genetic differences previously reported in ewe plasma melatonin concentrations were correlated with differences in the synthesis and release of other 5-methoxyindoles. To determine if 5-methoxytryptophol (5-ML), which is known to be present in large amounts in the sheep pineal gland, is released, as is melatonin, into the general circulation, and if some temporal relationships between 5-ML and melatonin release could be observed, two groups of ewes were selected with respect to their endogenous melatonin secretion: in the first experiment, ten ewes from the low melatonin group (low group) and ten ewes from the high melatonin group (high group). 5-ML was measured every hour during a 24-hr period by radioimmunoassay. In all ewes, 5-ML was released during day-time, the rhythm of 5-ML concentrations being inversely related with the melatonin rhythm. Both day-time and night-time 5-ML concentrations were higher in the ewes from the high group than in the ewes from the low group (14.7 +/- 1.0 pg/mL plasma versus 6.4 +/- 0.3 pg/mL plasma during the day, 3.1 +/- 0.2 pg/mL plasma versus 1.9 +/- 0.2 pg/mL plasma during the night). The 5-ML/melatonin ratio appeared much higher during the day than during the night but was very similar in both groups (day-time: 1.03 in the high group versus 1.16 in the low group, night-time: 0.01 in both groups). In a second experiment, six low group and seven high group ewes were submitted to 1 hr of extra light at night. 5-ML increased and melatonin decreased during extra light. Our results clearly show for the first time a daily variation in circulating 5-ML, and that the strong genetic contribution in the variability in melatonin concentrations in sheep are clearly correlated with a similar variability in 5-ML concentrations. Whether 5-ML, like melatonin, plays a physiological role in the different adaptation processes to the environment remains to be determined.

Morning administration of melatonin antagonizes the antigonadotrophic effect of afternoon injections of melatonin, 5-methoxytryptophol and arginine vasotocin in intact mice

In intact prepubertal mice kept under a long photoperiod subcutaneous afternoon (4:30 p.m.) injections (20 micrograms) but not morning (9:30 a.m.) injections (100 micrograms) of melatonin and 5-methoxytryptophol elicited antigonadotrophic effects. A morning dose (100 micrograms) of methoxytryptophol abolished the antigonadotrophic effects of afternoon injections of methoxytryptophol. Similarly the antigonadotrophic effects of afternoon injections of melatonin, 5-methoxytryptophol and arginine vasotocin could be partially destroyed by 100 micrograms and completely abolished by 1 mg melatonin administered in the morning.

Effects of retinal and pineal low molecular weight fractions and antipsychotic drugs on hydroxyindole-O-methyltransferase

Fractions from bovine retinas and sheep pineals of low molecular weight decrease the activity of purified hydroxyindole-O-methyltransferase (HIOMT). The antipsychotic drugs chlorpromazine and haloperidol show a similar effect under the same experimental conditions. It is suggested that they may imitate the effect of (an) unknown natural suppressor(s) of HIOMT-activity, present in retina and pineal, decreasing the biosynthesis of methoxyindoles.

Inhibition of avian and mammalian hydroxy-indole-o-methyl-transferase (HIOMT) with low molecular weight fractions of mammalian pineal glands

Partially purified fractions from sheep pineal gland extracts, which show a fluorescence like pteridines, were shown to suppress the enzyme hydroxy-indole-o-methyltransferase (HIOMT) isolated from avian pineals and retinas. The results described demonstrate that the mechanism of inhibition of HIOMT activity is independent of the species and organ. A blocking effect was found in experiments whether retinal or pineal HIOMT were used and the effect was found as well with bovine HIOMT. It is shown that low molecular weight molecules show inhibitory activity and accompany the high molecular weight enzyme HIOMT.

Pineal melatonin rhythm: reduction in aging Syrian hamsters

The melatonin content measured by radioimmunoassay of the pineal gland over a 24-hour period (a light:dark cycle of 14 hours of light and 10 of darkness) was compared in young and old female and male Syrian hamsters. The young animals of both sexes exhibited roughly an eightfold rise in pineal melatonin during the dark phase of the cycle, whereas in the old hamsters the nocturnal rise in melatonin was almost completely absent. The results indicate a marked drop in pineal biosynthetic activity in the aging hamster.

Continued chemical and physiological studies with antigonadotropic fractions from extracts of bovine pineal glands

A variety of experiments carried out in recent years are reviewed and evidence is presented for the presence of non-indolic, pineal antigonadotropic substances in pineal extracts and partially purified pineal fractions. Other data are presented suggesting the presence of prolactin releasing and release-inhibiting substances in bovine pineal glands. Also, the sulfur-containing amino acid and putative neurotransmitter taurine was found in large quantities in bovine pineals closely associated with fractions possessing antigonadotropic activity.

A survey of the location, isolation and identification of indoles, pteridines and some unknown active substances in sheep pineals. The possible significance of pteridines for the neuroendocrine control of neoplastic growth

Several indoles with mass spectra identical to those of synthetic melatonin, 5-hydroxyindole-3-acetic acid (5-HIAA), 5-methoxyindole-3-acetic acid (5-MIAA), 5-hydroxytryptophol (5-HTL) and 5-methoxytryptophol (5-MTL) could be located, isolated and identified in sheep pineal extracts using rather simple and mild extraction and separation methods. An antigonadotropin, which differs from melatonin, was isolated and partially purified from sheep pineals, using compensatory ovarian hypertrophy after unilateral ovariectomy as a bioassay. Antigonadotropic and gonadotropic compounds which differ from the indoles above mentioned could be located with the same methods. In vitro, these fractions act either on the hypothalamus or on the anterior pituitary. From the paper chromatography fraction, acting on the anterior pituitary in vitro, a compound could be isolated which is most probably identical with biopterin. In our opinion, however, this compound is not responsible for the antigonadotropic activity of the fraction, observed in vitro. Some pineal fractions showing an effect on the activity of the hypothalamus or anterior pituitary of male rats and mice in vitro, may be also active in some experimental tumour models. A possible relationship between disorders in pteridine metabolism and neoplastic growth is discussed.

Neuroendocrine function in long-term pinealectomized male rats, following visual and audiogenic stress

Intact, sham-pinealectomized and pinealectomized adult male rats were maintained for 10 weeks on a light : dark (L : D) cycle of 12 : 12,with lights on at 6 a.m. Subsequently they were acutely exposed to (1) visual or (2) audiogenic stress for periods of 2 or 30 min, immediately following which they were decapitated and serum ACTH, corticosterone, FHS, LH, PRL and TSH concentrations were determined. Serum ACTH and corticosterone levels were similar in control and operated groups following both types of stresses. Serum FSH and LH concentrations were elevated in pinealectomized animals as compared to controls, following 30 min of exposure to visual stimulation; no difference in these parameters was observed between the groups following audiogenic stress. Serum PRL levels tended to be lower in pinealectomized animals following both stresses. Serum TSH concentrations following visual stimulation were similar in all groups, but audiogenic stimulation resulted in elevated TSH levels as compared to controls. These data demonstrate that the pineal gland plays an integral role in the responses of the parvicellular neuroendocrine axes to acute neurogenic stress. Possible molecular bases for this involvement are discussed.