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Abstract
In order to evaluate melatonin implication in the regulating of its own secretory process by pinealocytes, we used morphometric techniques for transmission electron microscopy. In mice treated with 100 mg of melatonin (N-acetyl-5-methoxy-tryptamine) by daily subcutaneous injection, we observed a decrease in number and volumetric density of lysosomes. Our results showed that melatonin influences the secretory activity of pinealocytes and participates in a complex secretory regulating mechanism.
Highlights
The synthesis of melatonin (N-acetyl-5-methoxy-tryptamine) takes place in several tissues, especially in the pineal gland and retina, where one can observe that its synthesis is rhythmic (Cassone & Natesan, 1997)
In the group treated with melatonin we observed a decrease in the number and volumetric density of dense-core vesicles and an increase in the number and volumetric fractions of lipid droplets and Golgi apparatus
The dense-core vesicles are frequent in pinealocytes of mice and their enclosed flocculent material, which is believed to be proteinaceous in nature, and may contain active peptides, serotonin, melatonin and other pineal indoles (Vollrath, 1984)
Summary
The synthesis of melatonin (N-acetyl-5-methoxy-tryptamine) takes place in several tissues, especially in the pineal gland and retina, where one can observe that its synthesis is rhythmic (Cassone & Natesan, 1997). We do not know the precise sites of interaction between melatonin and the neuroendocrine system, its activity involves the hypothalamus, hypophysis, gonads, and the pineal gland itself (Reiter, 1995). The secretory activity of melatonin involves the endoplasmic reticulum, Golgi apparatus, lysosomes, and dense-core vesicles, which may be considered as morphological indicators of secretory activity of the pineal gland (Reiter, 1981). Melatonin secretion is regulated by photoperiod alterations that reach the pineal gland through polysynaptic pathways which leave the retinohy-.
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Schedule a callMore From: Brazilian journal of biology = Revista brasleira de biologia
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