Blanco Montserrat, Gallego Rosalía, García-Caballero Tomás, Diéguez Carlos, Beiras Andrés
Department of Morphological Sciences, School of Medicine and University Clinical Hospital, University of Santiago de Compostela, C/ San Francisco, 15782 Santiago de Compostela, Spain.
Histochem Cell Biol. 2003 Oct;120(4):259-64. doi: 10.1007/s00418-003-0562-z. Epub 2003 Aug 28.
Orexins A and B are hypothalamic peptides derived from a precursor called prepro-orexin and are associated with the stimulation of food intake and arousal. There is evidence that orexins act on some pituitary functions. Since no studies have been done concerning the presence of orexins in human pituitary, it is unclear whether the local effect of these peptides is due to orexins synthesized in the pituitary or to circulating-derived orexins. To define a possible paracrine regulatory role of orexins on pituitary cell function, we have sought to characterize the expression of orexins in the human adenohypophysis as well as to identify the cell types that express these proteins. In the present study, we used immunohistochemistry and double labeling to detect the presence of orexin A and orexin B in human pituitary. Orexin A was localized in 33% of pituitary cells. With double immunofluorescence techniques we demonstrated that orexin A is present in PRL (82 +/- 5.3%), TSH (18 +/- 2.3%), GH (10 +/- 2.3%), FSH (8 +/- 2.6%), and LH (7 +/- 3.2%) cells, but not in corticotroph cells. Orexin B was found in virtually all corticotrophs cells of the anterior pituitary. These results demonstrate that lactotroph cells are the main source of orexin A and corticotroph cells of orexin B. In summary the present findings provide the first evidence that orexins A and B are expressed in specific human pituitary cell types. Our data provide the cellular basis for a paracrine role of orexins in human pituitary cell function and further our understanding regarding the mechanisms by which orexins influence neuroendocrine function.
食欲素A和B是源自一种名为前食欲素原的前体的下丘脑肽，与食物摄入刺激和觉醒有关。有证据表明食欲素作用于某些垂体功能。由于尚未对人类垂体中食欲素的存在进行研究，尚不清楚这些肽的局部作用是由于垂体中合成的食欲素还是循环来源的食欲素。为了确定食欲素对垂体细胞功能可能的旁分泌调节作用，我们试图表征食欲素在人腺垂体中的表达，并鉴定表达这些蛋白质的细胞类型。在本研究中，我们使用免疫组织化学和双重标记来检测人垂体中食欲素A和食欲素B的存在。食欲素A定位于33%的垂体细胞中。通过双重免疫荧光技术，我们证明食欲素A存在于催乳素（PRL，82±5.3%）、促甲状腺激素（TSH，18±2.3%）、生长激素（GH，10±2.3%）、促卵泡激素（FSH，8±2.6%）和促黄体生成素（LH，7±3.2%）细胞中，但不存在于促肾上腺皮质激素细胞中。在前垂体的几乎所有促肾上腺皮质激素细胞中都发现了食欲素B。这些结果表明，催乳素细胞是食欲素A的主要来源，促肾上腺皮质激素细胞是食欲素B的主要来源。总之，本研究结果首次证明食欲素A和B在特定的人垂体细胞类型中表达。我们的数据为食欲素在人垂体细胞功能中的旁分泌作用提供了细胞基础，并进一步加深了我们对食欲素影响神经内分泌功能机制的理解。
