title: Effects of melatonin in connection with the antioxidant defense system in the gills of the estuarine crab Neohelice granulata.
abstract: Numerous studies have shown that melatonin exerts some influence on the antioxidant defense system (ADS) in vertebrates, but for crustaceans no such effect has been demonstrated till now. However, earlier reports did show a similar profile of daily variations in the ADS of the gills and the melatonin content of the eyestalk in the crab Neohelice granulata and, thus, the aim of this study was to take a closer look at the effects of melatonin in the gill ADS of N. granulata. Gill ADS is to a minor extent modulated by reactive oxygen species (ROS), because only the nonproteic sulfhydryl (NP-SH) content increases (p<0.05) in the presence of hydrogen peroxide (H(2)O(2)). No significant differences (p>0.05) were observed in the melatonin content of the hemolymph between intact and eyestalkless crabs. Gills from intact and eyestalkless crabs injected with physiological saline showed a daily variation in the total peroxyl radical scavenging capacity (TPRSC) (p<0.05) with two peaks, one at the photophase and another at the scotophase. However, in the gills of eyestalkless crabs injected with melatonin (2 x 10(-12)mol crab(-1)), the daily variation in TPRSC values was abolished (p>0.05). This molecule did not change the NP-SH content (p>0.05) in vitro, but decreased (p<0.05) the oxygen consumption in gills when incubated for 120 min. In the in vivo experiments melatonin also decreased (p<0.05) the oxygen consumption in eyestalkless crabs after 390 min. The results suggest that melatonin does not act directly on the ADS of the gills of N. granulata, but decreases the aerobic metabolism possibly involved in variations of tissue ADS.
authors.affiliation: Programa de Pós-Graduação em Ciências Fisiológicas - Fisiologia Animal Comparada, Instituto de Ciências Biológicas, Universidade Federal do Rio Grande - FURG, Rio Grande, RS, Brazil. maciel-fe@hotmail.com
authors.forename: Fábio Everton
authors.initials: FE
authors.lastname: Maciel
authors.forename: Bianca Padovani
authors.initials: BP
authors.lastname: Ramos
authors.forename: Márcio Alberto
authors.initials: MA
authors.lastname: Geihs
authors.forename: Marcelo Alves
authors.initials: MA
authors.lastname: Vargas
authors.forename: Bruno Pinto
authors.initials: BP
authors.lastname: Cruz
authors.forename: Victor Benno
authors.initials: VB
authors.lastname: Meyer-Rochow
authors.forename: Olli
authors.initials: O
authors.lastname: Vakkuri
authors.forename: Silvana
authors.initials: S
authors.lastname: Allodi
authors.forename: José Maria
authors.initials: JM
authors.lastname: Monserrat
authors.forename: Luiz Eduardo Maia
authors.initials: LE
authors.lastname: Nery
mesh_terms: D000332:Aerobiosis; D000818:Animals; D000975:Antioxidants / Q000378:metabolism*; D003386:Brachyura / Q000187:drug effects* / Q000378:metabolism*; D005880:Gills / Q000187:drug effects* / Q000378:metabolism*; D006458:Hemolymph / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008550:Melatonin / Q000378:metabolism / Q000494:pharmacology*; D018384:Oxidative Stress / Q000187:drug effects
chemical_list: D000975:Antioxidants; D006861:Hydrogen Peroxide; D008550:Melatonin