{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,22]],"date-time":"2026-09-22T08:31:23Z","timestamp":1790065883956,"version":"4.0.1"},"reference-count":51,"publisher":"The Company of Biologists","issue":"6","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2011,3,15]]},"abstract":"<jats:p>Melatonin has been suggested to play a role in fish osmoregulation, and in salmonids has been related to the timing of adaptive mechanisms during smolting. It has been described that acclimation to different environmental salinities alters levels of circulating melatonin in a number of fish species, including rainbow trout. However, nothing is known regarding salinity effects on melatonin synthesis in the pineal organ, which is the main source of rhythmically produced and secreted melatonin in blood. In the present study we have evaluated, in rainbow trout, the effects of acclimation to different salinities on day and night plasma melatonin values and pineal organ melatonin synthesis. Groups of freshwater (FW)-adapted rainbow trout were placed in tanks with four different levels of water salinity (FW, 6, 12, 18 p.p.t.; parts per thousand) and maintained for 6 h or 5 days. Melatonin content in plasma and pineal organs, as well as the pineal content of serotonin (5-HT) and its main oxidative metabolite (5-hydroxyindole-3-acetic acid; 5-HIAA) were measured by high performance liquid chromatography. In addition, day\u2013night changes in pineal organ arylalkylamine N-acetyltransferase (AANAT2) activity and aanat2 gene expression were studied. Plasma osmolalities were found to be higher in rainbow trout exposed to all salinity levels compared with the control FW groups. A salinity-dependent increase in melatonin content was found in both plasma and pineal organs. This effect was observed during the night, and was related to an increase in aanat2 mRNA abundance and AANAT2 enzyme activity, both of which also occurred during the day. Also, the levels of indoles (5-HT, 5-HIAA) in the pineal organ were negatively affected by increasing water salinity, which seems to be related to the higher recruitment of 5-HT as a substrate for the increased melatonin synthesis. A stimulatory effect of salinity on pineal aanat2 mRNA expression was also identified. These results indicate that increased external salinity promotes melatonin synthesis in the pineal organ of rainbow trout by enhancing synthesis of AANAT protein independently of its regulation by light. The possibility that pineal melatonin is a target for hormones involved in the response of fish to osmotic challenge is discussed, as well as the potential role of melatonin in the timing of osmoregulatory processes.<\/jats:p>","DOI":"10.1242\/jeb.051516","type":"journal-article","created":{"date-parts":[[2011,2,23]],"date-time":"2011-02-23T18:13:48Z","timestamp":1298484828000},"page":"928-936","source":"Crossref","is-referenced-by-count":29,"title":["Changes in plasma melatonin levels and pineal organ melatonin synthesis following acclimation of rainbow trout (<i>Oncorhynchus mykiss<\/i>) to different water salinities"],"prefix":"10.1242","volume":"214","author":[{"given":"Marcos A.","family":"L\u00f3pez-Pati\u00f1o","sequence":"first","affiliation":[{"name":"Departamento de Biolox\u00eda Funcional e Ciencias da Sa\u00fade, Facultade de Biolox\u00eda, Universidade de Vigo, 36310 Vigo, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Arnau","family":"Rodr\u00edguez-Illamola","sequence":"additional","affiliation":[{"name":"Departamento de Biolox\u00eda Funcional e Ciencias da Sa\u00fade, Facultade de Biolox\u00eda, Universidade de Vigo, 36310 Vigo, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Manuel","family":"Gesto","sequence":"additional","affiliation":[{"name":"Departamento de Biolox\u00eda Funcional e Ciencias da Sa\u00fade, Facultade de Biolox\u00eda, Universidade de Vigo, 36310 Vigo, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jos\u00e9 L.","family":"Soengas","sequence":"additional","affiliation":[{"name":"Departamento de Biolox\u00eda Funcional e Ciencias da Sa\u00fade, Facultade de Biolox\u00eda, Universidade de Vigo, 36310 Vigo, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jes\u00fas M.","family":"M\u00edguez","sequence":"additional","affiliation":[{"name":"Departamento de Biolox\u00eda Funcional e Ciencias da Sa\u00fade, Facultade de Biolox\u00eda, Universidade de Vigo, 36310 Vigo, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"237","reference":[{"key":"2021042506291691600_R1","doi-asserted-by":"crossref","first-page":"905","DOI":"10.1210\/endo.139.3.5790","article-title":"Transcripts encoding two melatonin synthesis enzymes in the teleost pineal organ: circadian regulation in pike and zebrafish, but not in trout","volume":"139","author":"B\u00e9gay","year":"1998","journal-title":"Endocrinology"},{"key":"2021042506291691600_R2","doi-asserted-by":"crossref","first-page":"255","DOI":"10.1097\/00001756-200002070-00006","article-title":"Melatonin synthesis: arylalkylamine N-acetyltransferases in trout retina and pineal organ are different","volume":"11","author":"Benyassi","year":"2000","journal-title":"NeuroReport"},{"key":"2021042506291691600_R3","first-page":"1","article-title":"Glucocorticoid receptors and serotonin N-acetyltransferase activity in the fish pineal organ","volume":"12","author":"Benyassi","year":"2001","journal-title":"Neuroendocrinology"},{"key":"2021042506291691600_R4","doi-asserted-by":"crossref","first-page":"61","DOI":"10.1029\/CE043p0061","article-title":"Seawater adaptation strategies in salmonids","volume-title":"Aquaculture: Fundamentals and Applied Research. 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Physiol."},{"key":"2021042506291691600_R31","doi-asserted-by":"crossref","first-page":"141","DOI":"10.1023\/A:1007808924841","article-title":"Diel changes in plasma arginine vasotocin, isotocin, and melatonin in rainbow trout (Oncorhynchus mykiss)","volume":"21","author":"Kulczykowska","year":"1999","journal-title":"Fish Physiol. Biochem."},{"key":"2021042506291691600_R32","doi-asserted-by":"crossref","first-page":"201","DOI":"10.1023\/A:1014079917644","article-title":"Responses of circulating arginine vasotocin, isotocin, and melatonin to osmotic and disturbance stress in rainbow trout (O. mykiss)","volume":"24","author":"Kulczykowska","year":"2001","journal-title":"Fish Physiol. 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B"},{"key":"2021042506291691600_R35","doi-asserted-by":"crossref","first-page":"175","DOI":"10.1007\/BF00802755","article-title":"Time course of osmotic adaptation and gill energetics of rainbow trout (Salmo gairdneri R) following abrupt changes in external salinity","volume":"144","author":"Leray","year":"1981","journal-title":"J. Comp. Physiol."},{"key":"2021042506291691600_R36","doi-asserted-by":"crossref","first-page":"195","DOI":"10.1016\/j.ygcen.2006.03.002","article-title":"Effects of acute stress on osmoregulation, feed intake, IGF-1, and cortisol in yearling steelhead trout (Oncorhynchus mykiss) during seawater adaptation","volume":"148","author":"Liebert","year":"2006","journal-title":"Gen. Comp. Endocirnol."},{"key":"2021042506291691600_R37","doi-asserted-by":"crossref","first-page":"180","DOI":"10.1016\/j.cbpa.2006.02.031","article-title":"Melatonin effects on food intake and activity rhythms in two fish species with different activity patterns: diurnal (goldfish) and nocturnal (tench)","volume":"144A","author":"L\u00f3pez-Olmeda","year":"2006","journal-title":"Comp. Biochem. Physiol."},{"key":"2021042506291691600_R38","doi-asserted-by":"crossref","first-page":"486","DOI":"10.1016\/j.cbpa.2008.12.003","article-title":"Effects of water salinity on melatonin levels in plasma and peripheral tissues and on melatonin binding sites in European sea bass (Dicentrarchus labrax)","volume":"152A","author":"L\u00f3pez-Olmeda","year":"2009","journal-title":"Comp. Biochem. Physiol."},{"key":"2021042506291691600_R39","unstructured":"L\u00f3pez-Pati\u00f1o\n              M. A.\n            \n           (2004). Receptores Centrales y Perif\u00e9ricos de Melatonina en el Tele\u00f3steo Tinca tinca. Caracterizaci\u00f3n, Farmacolog\u00eda y Ritmicidad Diaria y Estacional. PhD thesis, Universidad Complutense de Madrid, Madrid, Spain."},{"key":"2021042506291691600_R40","doi-asserted-by":"crossref","first-page":"92","DOI":"10.1016\/j.cbpa.2007.10.016","article-title":"High density and food deprivation affect arginine vasotocin, isotocin and melatonin in gilthead sea bream (Sparus auratus)","volume":"149A","author":"Mancera","year":"2008","journal-title":"Comp. Biochem. Physiol."},{"key":"2021042506291691600_R41","doi-asserted-by":"crossref","first-page":"3","DOI":"10.1016\/j.ygcen.2005.12.009","article-title":"Hormonal control of salt and water in vertebrates","volume":"147","author":"McCormick","year":"2006","journal-title":"Gen. Comp. 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B"},{"key":"2021042506291691600_R44","doi-asserted-by":"crossref","first-page":"84","DOI":"10.1016\/j.cbpa.2009.10.006","article-title":"Effect of cortisol on melatonin production by the pineal organ of tilapia, Oreochromis mossambicus","volume":"155A","author":"Nikaido","year":"2010","journal-title":"Comp. Biochem. 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J. Physiol."},{"key":"2021042506291691600_R48","doi-asserted-by":"crossref","first-page":"325","DOI":"10.1111\/j.1365-2109.2007.01677.x","article-title":"Melatonin treatment affects the osmoregulatory capacity of rainbow trout","volume":"38","author":"Sangiao-Alvarellos","year":"2007","journal-title":"Aquac. Res."},{"key":"2021042506291691600_R49","doi-asserted-by":"crossref","first-page":"240","DOI":"10.1016\/j.ygcen.2005.06.007","article-title":"Altered plasma and pituitary arginine vasotocin and hypothalamic provasotocin expression in flounder (Platichthys flesus) following hypertonic challenge and distribution of vasotocin receptors within the kidney","volume":"144","author":"Warne","year":"2005","journal-title":"Gen. Comp. Endocrinol."},{"key":"2021042506291691600_R50","doi-asserted-by":"crossref","first-page":"591","DOI":"10.1152\/physrev.1997.77.3.591","article-title":"The stress response in fish","volume":"77","author":"Wendelaar-Bonga","year":"1997","journal-title":"Physiol. Rev."},{"key":"2021042506291691600_R51","doi-asserted-by":"crossref","first-page":"149","DOI":"10.1007\/978-1-4615-3042-8_12","article-title":"Melatonin and its effects in fishes: an overview","volume-title":"Rhythms in Fishes","author":"Zachmann","year":"1992"}],"container-title":["Journal of Experimental Biology"],"original-title":[],"language":"en","link":[{"URL":"http:\/\/journals.biologists.com\/jeb\/article-pdf\/214\/6\/928\/1441724\/928.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"http:\/\/journals.biologists.com\/jeb\/article-pdf\/214\/6\/928\/1441724\/928.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2021,4,25]],"date-time":"2021-04-25T07:17:13Z","timestamp":1619335033000},"score":1,"resource":{"primary":{"URL":"https:\/\/journals.biologists.com\/jeb\/article\/214\/6\/928\/10641\/Changes-in-plasma-melatonin-levels-and-pineal"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2011,3,15]]},"references-count":51,"journal-issue":{"issue":"6","published-print":{"date-parts":[[2011,3,15]]}},"URL":"https:\/\/doi.org\/10.1242\/jeb.051516","relation":{},"ISSN":["1477-9145","0022-0949"],"issn-type":[{"value":"1477-9145","type":"electronic"},{"value":"0022-0949","type":"print"}],"subject":[],"published":{"date-parts":[[2011,3,15]]}}}