New actions of melatonin and their relevance to biometeorology

Abstract

Melatonin is not only produced by the pineal gland, retina and parietal but also by various other tissues and cells from vertebrates, invertebrates, fungi, plants, multicellular algae and by unicells. In plants, many invertebrates and unicells, its concentration often exceeds that found in vertebrate blood by several orders of magnitude. The action of melatonin is highly pleiotropic. It involves firstly, direct effects, via specific binding sites in various peripheral tissues and cells of vertebrates, including immunomodulation; secondly, systemic influences on the cytoskeleton and nitric oxide formation, mediated by calmodulin; and thirdly, antioxidative protection, perhaps also in the context of photoprotection in plants and unicells. In some dinoflagellates, melatonin conveys temperature signals. On the basis of these comparisons, melatonin appears to mediate and modulate influences from several major environmental factors, such as the photoperiod, radiation intensity and temperature.

Environmental effects on asexual reproduction rates of the scyphozoan Aurelia labiata

“…Boeuf & Falcon 2001, Farnsworth 2004. Melatonin regulates circadian rhythms and photoperiodism throughout the animal kingdom from protozoans to mammals (reviewed by Hardeland 1997, Pandi-Perumal et al 2006. In many animals, light and temperature interact to regulate melatonin (Balzer & Hardeland 1996).…”

“…reproduction) rhythms, and for orientation and navigation of many organisms (e.g. Honegger et al 1980, Hamner et al 1994, Hardeland 1997, Naylor 2006. The amount of sunlight that reaches the Earth's surface is changing due to the effects of human activities (Pallé & Butler 2002, Wild et al 2005.…”

The Effect of Melatonin on Liver Superoxide Dismutase Activity, Serum Nitrate and Thyroid Hormone Levels.

“…It involves: firstly, direct effects via spesific binding sites in various peripheral tissues and cells of vertebrates, including immunomodulation; secondly, systemic influence on the cytoskeleton and nitric oxide formation, mediated by calmodulin; and thirdly, antioxidative protection [13].…”

Estudo da presença, da função e das vias de produção da melatonina em invertebrados.

“…No protista dinoflagelado Lingulodinium polyedrum, por exemplo, foram verificados picos noturnos do indol, e a melatonina seria capaz de induzir encistamento em resposta a um decréscimo da temperatura, independentemente do fotoperíodo (21,22). A presença de melatonina com um pico noturno foi verificada também em outros Protistas, como Euglena (23), algas verdes (24), vermes platelmintes (25) e insetos como a mosca Drosophila melanogaster (26).…”

“…No ensífero Gryllus bimaculatus há picos noturnos no cérebro e nos olhos compostos, e picos diurnos nos apêndices locomotores, antenas e órgão ovopositor (30). No molusco gastrópode Aplysia californica a situação é semelhante, com pico noturno de melatonina no cérebro e pico diurno no olho (31), estrutura na qual a melatonina parece ter um papel fotoprotetor (22).…”