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Exogenously administered melatonin causes a 2-fold rise in glutathione peroxidase activity within 30 min in the brain of the rat. Furthermore, brain glutathione peroxidase activity is higher at night than during the day and is correlated with high night-time tissue melatonin levels. Glutathione peroxidase is thought to be the principal enzyme eliminating(More)
Melatonin was recently shown to be a component of the antioxidative defense system of organisms due to its free radical scavenging and antioxidant activities. Pharmacologically, melatonin stimulates the activity of the peroxide detoxifying enzyme glutathione peroxidase in rat brain and in several tissues of chicks. In this report, we studied the endogenous(More)
Pineal melatonin secretion exhibits a rhythm which is identified as a circadian cycle with a period of between 20 and 28 h in most animals. The melatonin rhythm has an acrophase of about -30 degrees. The aim of this study was determine the effect of lithium on the melatonin rhythm since lithium is usually used as a therapeutic agent in manic-depressive(More)
The diurnal variations in the contents of nitric oxide (NO) and cyclic GMP were studied in the chick brain. NO and cyclic GMP contents in the chick brain were lower at night than during the day and were inversely correlated with high night-time tissue melatonin levels. Furthermore, when animals were kept in light at night, tissue melatonin levels remained(More)
Estrogen effects on pineal secretion of melatonin are controversial. Some feel that estrogen inhibits melatonin output in vitro but not in vivo. Melatonin levels vary with the age in chickens where circulating estrogen levels also vary. Laying hens have minimal melatonin levels and maximal serum iron concentrations. Thus, we reasoned that iron released by(More)
The ability of melatonin to influence lipopolysaccharide (LPS)-induced genotoxicity was tested using micronuclei as an index in both bone marrow and peripheral blood cells of rats. LPS was given as a single dose of 10 mg/kg. Melatonin (5 mg/kg) was injected prior to LPS administration and thereafter at 6 h intervals to the conclusion of the study (72 h).(More)
We have recently described, using perifused pineal glands, that calcium influx participates in the activation of chick pineal gland. This study shows that the loss of perifused chick pineal gland activity is a complex process which seems to involve the release of calcium from intracellular stores, calmodulin and calcium-activated neutral protease (CANP).(More)
This paper describes the influence of iron on both nuclear and cytosolic melatonin contents in several tissues of chicks. The neurohormone melatonin was estimated by means of radioimmunoassay. Iron, administered as FeCl3, decreased the nuclear melatonin level in a variety of tissues, including brain, heart, lung, kidney, and erythrocytes (nucleated cells in(More)
Melatonin is the neurohormone which is synthesized by the pineal gland and secreted rhythmically. The role of calcium in the activation of melatonin production remains unknown. In this study, we demonstrated that calcium input participates in the regulation of chick pineal gland. Pineal glands from Gallus domesticus were perifuse with Krebs medium(More)
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