title: Heterogeneity of growth hormone immunoreactivity in lymphoid tissues and changes during ontogeny in domestic fowl.
abstract: Growth hormone (GH) expression is not confined to the pituitary and occurs in many extrapituitary tissues. Here, we describe the presence of GH-like moieties in chicken lymphoid tissues and particularly in the bursa of Fabricius. GH-immunoreactivity (GH-IR), determined by ELISA, was found in thymus, spleen, and in bursa of young chickens, but at concentrations <1% of those in the pituitary gland. Although the GH concentration in the spleen and bursa was approximately 0.82 and 0.23% of that in the pituitary at 9-weeks of age, because of their greater mass, the total GH content in the spleen, bursa, and in thymus were 236, 5.18, and 31.5%, respectively, of that in the pituitary gland. This GH-IR was associated with several proteins of different molecular size, as in the pituitary gland, when analyzed by SDS-PAGE under reducing conditions. While most of the GH-IR in the pituitary was associated with the 26 kDa monomer (40%), the putatively glycosylated 29 kDa variant (16%), the 52 kDa dimer (14%) and the 15 kDa submonomeric isoform (16%), GH-IR in the lymphoid tissues was primarily associated (27-36%) with a 17 kDa moiety, although bands of 14, 26, 29, 32, 37, 40, and 52 kDa were also identified in these tissues. The heterogeneity pattern and relative abundance of bursal GH-IR bands were determined during development between embryonic day 13 (ED13) and 9-weeks of age. The relative proportion of the 17 kDa GH-like band was higher (45-58%) in posthatched birds than in the 15 and 18-day old embryos (21 and 19%, respectively). The 26 kDa isoform was minimally present in embryos (<4% of total GH-IR) but in posthatched chicks it increased to 12-20%. Conversely, while GH-IR of 37, 40, and 45 kDa were abundantly present in embryonic bursa ( approximately 30% at ED13 and approximately 52-55% at ED15 and ED18, respectively), in neonatal chicks and juveniles they accounted for less than 5%. These ontogenic changes were comparable to those previously reported for similar GH-IR proteins in the chicken testis during development. In summary, these results demonstrate age-related and tissue-specific changes in the content and composition of GH in immune tissues of the chicken, in which GH is likely to be an autocrine or paracrine regulator.
authors.affiliation: Department of Cellular and Molecular Neurobiology, Institute of Neurobiology, Campus UNAM-UAQ Juriquilla, Universidad Nacional Autónoma de México, A.P. 1-1141, Querétaro, 76001, Mexico. lunam@servidor.unam.mx
authors.forename: M
authors.initials: M
authors.lastname: Luna
authors.forename: N
authors.initials: N
authors.lastname: Barraza
authors.forename: L
authors.initials: L
authors.lastname: Berumen
authors.forename: M
authors.initials: M
authors.lastname: Carranza
authors.forename: E
authors.initials: E
authors.lastname: Pedernera
authors.forename: S
authors.initials: S
authors.lastname: Harvey
authors.forename: C
authors.initials: C
authors.lastname: Arámburo
mesh_terms: D000818:Animals; D002060:Bursa of Fabricius / Q000378:metabolism; D002642:Chick Embryo; D002645:Chickens / Q000254:growth & development* / Q000378:metabolism*; D013006:Growth Hormone / Q000378:metabolism*; D007150:Immunohistochemistry; D008221:Lymphoid Tissue / Q000378:metabolism*; D010902:Pituitary Gland / Q000378:metabolism; D013154:Spleen / Q000378:metabolism; D013950:Thymus Gland / Q000378:metabolism
chemical_list: D013006:Growth Hormone