title: Evidence of melatonin synthesis in the ram reproductive tract.
abstract: Melatonin is a ubiquitous molecule found in a wide range of fluids, one of them being ram seminal plasma, in which it can reach higher concentrations than those found in blood, suggesting an extrapineal secretion by the reproductive tract. In order to identify the source of the melatonin found in ram seminal plasma, we first tried to determine whether the melatonin levels were maintained during the day. For this purpose, melatonin concentrations were measured in seminal plasma obtained from first ejaculates of six rams at 6:00 a.m. in total darkness, at 10:00 a.m. and at 14:00 p.m. The melatonin concentration was higher (p < 0.05) in ejaculates collected at 6:00 a.m. than at 10:00 and 14:00. There was no statistical difference between the latter. To further corroborate an extrapineal secretion of melatonin, the presence of the two key enzymes involved in melatonin synthesis, arylalkylamine-N-acetyltransferase (AANAT) and N-acetylserotonin-O-methyltransferase (ASMT) was analyzed by RT-PCR, q-PCR and Western-blot in ram testes, epididymis, and accessory glands. The RT-PCR showed the presence of the m-RNA codifying both AANAT and ASTM in all the tissues under study, but the q-PCR and Western-blot revealed that gene expression of these enzymes was significantly higher in the testis (p < 0.05). Immunohistochemistry confirmed the presence of AANAT and ASMT in the testis and revealed that they were found in the Leydig cells, spermatocytes, and spermatids. Also, measurable levels of melatonin were found in testicular tissue and the tail of the epididymis. In conclusion, our study indicates that the testes are one of the likely sources of the high levels of melatonin found in ram seminal plasma, at least during the day.
authors.affiliation: Grupo Biología y Fisiología de la Reproducción, Facultad de Veterinaria, Instituto de Investigación de Ciencias Ambientales de Aragón (IUCA), Universidad de Zaragoza, Zaragoza, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Gonzalez-Arto
authors.affiliation: Dpto. de Reprodução Animal, da Faculdade de Medicina Veterinaria e Zootecnia, da Universidade de São Paulo, São Paulo, Brazil.
authors.forename: T R dos S
authors.initials: TR
authors.lastname: Hamilton
authors.affiliation: Departamento de Patología Animal, Facultad de Veterinaria, Universidad de Zaragoza, Zaragoza, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Gallego
authors.affiliation: Grupo Biología y Fisiología de la Reproducción, Facultad de Veterinaria, Instituto de Investigación de Ciencias Ambientales de Aragón (IUCA), Universidad de Zaragoza, Zaragoza, Spain.
authors.forename: E
authors.initials: E
authors.lastname: Gaspar-Torrubia
authors.affiliation: Grupo Biología y Fisiología de la Reproducción, Facultad de Veterinaria, Instituto de Investigación de Ciencias Ambientales de Aragón (IUCA), Universidad de Zaragoza, Zaragoza, Spain.
authors.forename: D
authors.initials: D
authors.lastname: Aguilar
authors.affiliation: Grupo Biología y Fisiología de la Reproducción, Facultad de Veterinaria, Instituto de Investigación de Ciencias Ambientales de Aragón (IUCA), Universidad de Zaragoza, Zaragoza, Spain.
authors.forename: E
authors.initials: E
authors.lastname: Serrano-Blesa
authors.affiliation: Grupo Biología y Fisiología de la Reproducción, Facultad de Veterinaria, Instituto de Investigación de Ciencias Ambientales de Aragón (IUCA), Universidad de Zaragoza, Zaragoza, Spain.
authors.forename: J A
authors.initials: JA
authors.lastname: Abecia
authors.affiliation: Grupo Biología y Fisiología de la Reproducción, Facultad de Veterinaria, Instituto de Investigación de Ciencias Ambientales de Aragón (IUCA), Universidad de Zaragoza, Zaragoza, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Pérez-Pé
authors.affiliation: Grupo Biología y Fisiología de la Reproducción, Facultad de Veterinaria, Instituto de Investigación de Ciencias Ambientales de Aragón (IUCA), Universidad de Zaragoza, Zaragoza, Spain.
authors.forename: T
authors.initials: T
authors.lastname: Muiño-Blanco
authors.affiliation: Grupo Biología y Fisiología de la Reproducción, Facultad de Veterinaria, Instituto de Investigación de Ciencias Ambientales de Aragón (IUCA), Universidad de Zaragoza, Zaragoza, Spain.
authors.forename: J A
authors.initials: JA
authors.lastname: Cebrián-Pérez
authors.affiliation: Grupo Biología y Fisiología de la Reproducción, Facultad de Veterinaria, Instituto de Investigación de Ciencias Ambientales de Aragón (IUCA), Universidad de Zaragoza, Zaragoza, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Casao
mesh_terms: D000121:Acetylserotonin O-Methyltransferase / Q000378:metabolism*; D000818:Animals; D047068:Arylalkylamine N-Acetyltransferase / Q000378:metabolism*; D004822:Epididymis / Q000378:metabolism*; D007985:Leydig Cells / Q000378:metabolism; D008297:Male; D008550:Melatonin / Q000096:biosynthesis / Q000378:metabolism*; D012661:Semen / Q000378:metabolism*; D012756:Sheep; D013087:Spermatids / Q000378:metabolism; D013090:Spermatocytes / Q000378:metabolism; D013737:Testis / Q000166:cytology / Q000378:metabolism*
chemical_list: D000121:Acetylserotonin O-Methyltransferase; D047068:Arylalkylamine N-Acetyltransferase; D008550:Melatonin
keywords: AANAT; ASTM; extrapineal; seminal plasma; testes