Melatonin and Zinc

percyval577

basal and ganglia
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Both zinc deficiency and supplementation affect plasma melatonin levels in rats.
Bediz et al. 2003


Abstract (my paragraphing)
At physiological levels, zinc and various hormones affect each other reciprocally. Reduction in zinc levels in pinealectomized rats suggests the relation between zinc and melatonin. The effect of both zinc deficiency and supplementation on plasma melatonin levels in rats were investigated in this study.

The study was done in Selçuk University, Experimental Medicine Research and Application Center. Twenty-four adult male Sprague Dawley rats were divided into 3 groups. Eight rats were fed with zinc-deficient diet. Zinc supplementation was administered intaperitoneally to 8 rats. The remaining 8 rats were used as controls. All rats sacrificed 3 weeks later. Plasma melatonin and zinc levels were determined.

The plasma zinc levels of the zinc-supplemented group were higher than those of the other groups as expected (P<0.01). Similarly, the melatonin levels in the zinc-supplemented group were higher than those in the other groups.

A significant decrease was observed in melatonin levels of the zinc-deficient group compared to the control and zinc-supplemented group (P<0.01). The results of this study suggest that zinc deficiency decreases the melatonin levels and zinc supplementation may increase the plasma melatonin levels in rats.
paywalled
Acta Physiol Hung. 2003;90(4):335-9.
 
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percyval577

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Opposite effects of zinc and melatonin on thyroid hormones in rats.
Baltaci et al 2004


Abstract (my paragraphing)
The present study was conducted to investigate how thyroid function in rats is affected by administration of 3 mg per kg per day of zinc and/or melatonin.

The study was conducted with 40 Sprague-Dawley adult male rats equally divided into four groups: 1 (controls), 2 (zinc-only), 3 (melatonin-only) and 4 (zinc- and melatonin-supplemented). The supplementation was continued for 4 weeks after which the animals were sacrificed and plasma samples were obtained for determination of zinc, melatonin, free- and total triiodothyronine (T3), thyroxine (T4) and thyroid-stimulating hormone (TSH) levels.

The free T3, T4 and TSH levels were lower in the melatonin group than in all other groups (P<0.01), while free- and total T3 levels were higher in the zinc group (P<0.01). The group that received zinc and melatonin combined had free thyroid hormone levels higher than the only melatonin group.

These results show that melatonin has a thyroid function suppressing action, just the opposite to the actions of zinc. When zinc is administered along with melatonin, its thyroid function suppression is diminished.
paywalled
Toxicology. 2004 Jan 15;195(1):69-75.
 

percyval577

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Presence of links between zinc and melatonin during the circadian cycle in old mice: effects on thymic endocrine activity and on the survival.
Mocchegiani et al 1998


Abstract (my paragraphing)
Links between zinc and melatonin in old melatonin treated mice with a reconstitution of thymic functions have been recently documented. Concomitant increments of the nocturnal peaks of zinc and melatonin, with a synchronization of their circadian patterns, are achieved in old mice after melatonin treatment. A recovery of the nocturnal peaks of thymulin plasma levels and of the number of thymulin-secreting cells with a synchronization of their circadian patterns are also achieved.

The existence of significant positive correlations between melatonin and zinc and between melatonin and thymulin or the number of thymulin-secreting cells supports the presence of links between zinc and melatonin also during the circadian cycle with a beneficial effect on thymic functions. The altered circadian pattern of corticosteron in old mice is normalized by melatonin.

The existence of inverse correlations between corticosteron and melatonin, between corticosteron and zinc and between corticosteron and thymulin or the number of thymulin-secreting cells during the whole circadian cycle, suggests the involvement of glucocorticoids pathway in the melatonin thymic reconstitution, via zinc.

The presence of an interplay among zinc, melatonin, glucocorticoids and thymulin may be, therefore, supported during the circadian cycle. 'In vitro' experiments from old thymic explants show a direct action of zinc, rather than melatonin, on thymulin production, further suggesting that the action of melatonin on the thymic efficiency is mediated by the zinc bioavailability. The beneficial effect of the links between zinc and melatonin on thymic functions during the circadian cycle, may be extended to a prolonged survival in aging, where, however, zinc may be more involved.
paywalled
J Neuroimmunol. 1998 Jun 15;86(2):111-22.
 
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When you are already chronically ill you don't want to lower copper any further (macrophages need copper) which zinc does.

Melatonin on the other hand seems to be an electron donator to copper which turns bio-unavailable copper (II) to bio-available copper (I).