van der Kraan M, Adan R A, Entwistle M L, Gispen W H, Burbach J P, Tatro J B
Rudolf Magnus Institute for Neurosciences, Department of Medical Pharmacology, Utrecht University, The Netherlands.
Endocrinology. 1998 May;139(5):2348-55. doi: 10.1210/endo.139.5.6008.
Melanocortins (alphaMSH and ACTH-related peptides) influence the physiological functions of certain peripheral organs, including exocrine and endocrine glands. This study was designed to determine the identity and anatomical localization of the melanocortin receptors (MC-R) expressed in these organs in the rat. MC5-R messenger RNA was found in exocrine glands, including lacrimal, Harderian, preputial, and prostate glands and pancreas, as well as in adrenal gland, esophagus, and thymus, as demonstrated by ribonuclease protection assays. In exocrine glands, MC5-R messenger RNA expression was restricted to secretory epithelia. MC-R protein was likewise present in secretory epithelia of exocrine glands, as determined by 125I-labeled [Nle4,D-Phe7]alphaMSH ([125I]NDP-MSH) binding and autoradiography in tissue sections. Specific [125I]NDP-MSH binding was also observed in adrenal cortex, thymus, spleen, and esophageal and trachealis muscle. MC receptors in these sites are accessible to circulating MC-R agonists in vivo, as specific binding of [125I]NDP-MSH was observed in exocrine and adrenal glands after systemic injection in vivo. Taken together, these findings show that the MC5 receptor is commonly and selectively expressed in exocrine glands and other peripheral organs. Based on these findings and compelling evidence from other studies, a functional coherence is suggested between central and peripheral actions of melanocortins and melanocortin receptors in physiological functions, including thermoregulation, immunomodulation, and sexual behavior.
促黑素（α-促黑素及促肾上腺皮质激素相关肽）影响某些外周器官的生理功能，包括外分泌腺和内分泌腺。本研究旨在确定大鼠这些器官中表达的促黑素受体（MC-R）的特性及解剖定位。通过核糖核酸酶保护分析证明，在包括泪腺、哈德氏腺、包皮腺、前列腺和胰腺在内的外分泌腺以及肾上腺、食管和胸腺中发现了MC5-R信使核糖核酸。在外分泌腺中，MC5-R信使核糖核酸的表达局限于分泌上皮。通过组织切片中125I标记的[Nle4，D-Phe7]α-促黑素（[125I]NDP-MSH）结合及放射自显影测定，MC-R蛋白同样存在于外分泌腺的分泌上皮中。在肾上腺皮质、胸腺、脾脏以及食管和气管平滑肌中也观察到特异性的[125I]NDP-MSH结合。这些部位的MC受体在体内可被循环中的MC-R激动剂作用，因为在体内全身注射后，在外分泌腺和肾上腺中观察到了[125I]NDP-MSH的特异性结合。综上所述，这些发现表明MC5受体在外分泌腺和其他外周器官中普遍且选择性地表达。基于这些发现以及其他研究的有力证据，提示促黑素和促黑素受体在生理功能（包括体温调节、免疫调节和性行为）的中枢和外周作用之间存在功能上的一致性。
