New actions of meiatonin and their relevance to biometeorology

摘要

Meiatonin 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 pleiotro-pic. 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, meiatonin conveys temperature signals. On the basis of these comparisons, meiatonin appears to mediate and modulate influences from several major environmental factors, such as the photoperiod, radiation intensity and temperature.