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Melatonin was discovered to be a direct free radical scavenger less than 10 years ago. Besides its ability to directly neutralize a number of free radicals and reactive oxygen and nitrogen species, it stimulates several antioxidative enzymes which increase its efficiency as an antioxidant. In terms of direct free radical scavenging, melatonin interacts with(More)
This work evaluates whether physiological concentrations of the pineal secretory product melatonin contribute to the total antioxidant status (TAS) of human serum. Day and nighttime serum samples were collected from healthy volunteers ranging from 2 to 89 years of age and used to measure melatonin and TAS. Results showed that both melatonin and TAS in human(More)
The purpose of this study was to investigate the effect of melatonin, at pharmacological doses, on serum lipids of rats fed with a hypercholesterolemic diet. Therefore, different groups of animals were fed with either the regular Sanders Chow diet or a diet enriched in cholesterol. Moreover, animals were treated with or without melatonin in the drinking(More)
The regulation by alpha- and beta-adrenergic receptor agonists of rat pineal N-acetyltransferase (NAT) activity during development was studied. We found that isoproterenol, a beta-adrenergic agonist, exhibited a weak stimulatory effect on pineal NAT activity during the first 3 weeks of age. Indeed, the drug did not mimic the effect of darkness on pineal NAT(More)
In this report, rat hypothalamic nitric oxide synthase (NOS) activity is shown to be partially inhibited by physiological concentrations of the pineal hormone melatonin. In vitro studies demonstrate that 1 nM melatonin, which approximates the physiological concentration of the hormone at night, significantly inhibited NOS activity. In vivo studies show that(More)
Melatonin, the chief secretory product of the pineal gland, is a potent and efficient endogenous radical scavenger. Thus, melatonin was shown to protect different biomolecules, such as DNA, membrane lipids, and cytosolic proteins, from oxidative damage induced by oxygen-derived free radicals. In order to study the protective role of melatonin in hydrogen(More)
Melatonin binding sites were characterized in human blood lymphocytes. The specific binding 2-[125I]iodo-melatonin ([125I]MEL) to human lymphocytes was dependent on time and temperature, stability, saturation, and reversibility. Moreover, guanine nucleotides decreased the specific binding of [125I]MEL to crude membranes of human lymphocytes, suggesting the(More)
In the present study we have shown type II thyroxine 5'-deiodination (5'D) in the rat thymus. The enzyme activity was identified in crude extract homogenates by measuring the 125I released from [3',5'-125I]thyroxine which is used as a substrate of the reaction. The release of 125I is dependent on protein tissue concentration, time, temperature and pH, and(More)
In this paper, we summarize the results of in vitro studies showing that physiological concentrations of melatonin inhibit the norepinephrine-induced activation of prostaglandin E2 (PGE2) and cyclic AMP production in rat medial basal hypothalamus (MBH). Interestingly, a concentration of melatonin as low as 1 nM, which is roughly equivalent to the nocturnal(More)
Herein, we investigate the mechanisms involved in the adrenergically mediated stimulation of rat pineal N-acetyltransferase (NAT) activity during development using an in vitro model. Compared with adults, results suggest a different regulation of pineal NAT activity in growing rats where a similar efficiency of alpha- and beta-adrenergic receptor agonists(More)