Istituto di Anatomia Comparata dell'Università di Geneva, Viale Benedetto XV, 5, 16132 Geneva, Italy.
J Neuroendocrinol. 1989 Feb;1(1):53-60. doi: 10.1111/j.1365-2826.1989.tb00076.x.
Abstract The distribution of alpha-melanocyte-stimulating hormone (alpha-MSH)-like immunoreactivity in the central nervous system of the rainbow trout Salmo gairdneri was investigated by indirect immunofluorescence and peroxidase-antiperoxidase techniques, using a highly specific antiserum generated in rabbits against synthetic alpha-MSH. Immunoreactive perikarya were exclusively observed in the basal hypothalamus within the pars anterioris of the nucleus lateralis tuberis. In this region, a moderate number of small stained cell bodies were observed surrounding the dorsal wall of the anterior infundibular recess. These immunoreactive cells were organized in rostro-caudal rows extending over the whole portion of the nucleus. Positive fibres originating from these perikarya were visualized in the dorsal posterior lobe and the ventral hypothalamus. A dense tract of immunoreactive fibres projected ventrally through the pituitary stalk and terminated in the neurohypophysis. The concentrations of alpha-MSH in different regions of the brain were measured by means of a sensitive and specific radioimmunoassay. The dilution curves obtained with synthetic alpha-MSH and serial dilutions of diencephalon, mesencephalon, medulla oblongata, telencephalon or pituitary extracts were strictly parallel. The highest concentration of alpha-MSH in brain was found in the diencephalon (1.31 +/- 0.07 ng/mg protein). In contrast alpha-MSH was not detectable in cerebellar extracts. Reverse-phase high-performance liquid chromatography and radioimmunoassay were used to characterize alpha-MSH-like peptides in the trout brain and pituitary. Two major forms of immunoreactive alpha-MSH were resolved by high performance liquid chromatography in hypothalamic extracts; these peptides exhibited the same retention times as des-Na-acetyl alpha-MSH and its sulfoxide derivative, respectively. Additional peaks of alpha-MSH immunoreactive material were detected in pituitary extract. These latter peptides coeluted with authentic alpha-MSH, diacetyl alpha-MSH and their sulfoxide forms. These results provide the first evidence for the presence of alpha-MSH in the brain of a teleostean fish. Our data indicate that, in the brain, the immunoreactivity corresponds to the non-acetylated form of alpha-MSH, while three different types of alpha-MSH-like molecules (namely deacetylated, monoacetylated, and diacetylated forms) coexist in the pituitary. It thus appears that, in salmonoid fish, mono- or diacetylation of the N-terminal serine residue of aL-MSH only occurs at the pituitary level.
摘要 本研究采用间接免疫荧光和过氧化物酶-抗过氧化物酶技术，利用兔抗合成α-黑素细胞刺激素（α-MSH）的高特异性抗血清，研究了虹鳟鱼 Salmo gairdneri 中枢神经系统中α-MSH 样免疫反应物质的分布。免疫反应性神经元仅在前外侧核的前腹核区观察到。在这个区域，观察到大量围绕着前漏斗背壁的小染色细胞体。这些免疫反应细胞以延伸到整个核区的头尾排列成排。这些神经元的起源纤维在背侧后叶和腹侧下丘脑被可视化。一条密集的免疫反应纤维束通过垂体柄向腹侧投射，并终止于神经垂体。通过一种灵敏和特异的放射免疫测定法测量了不同脑区的 α-MSH 浓度。用合成的 α-MSH 和间脑、中脑、延髓、端脑或垂体提取物的连续稀释液获得的稀释曲线严格平行。脑内 α-MSH 的最高浓度出现在间脑（1.31±0.07ng/mg 蛋白）。相反，在小脑提取物中未检测到 α-MSH。反相高效液相色谱和放射免疫测定法用于鉴定虹鳟脑和垂体中的 α-MSH 样肽。在下丘脑提取物中，通过高效液相色谱分离出两种主要形式的免疫反应性 α-MSH；这些肽的保留时间分别与去乙酰化 α-MSH 和其亚砜衍生物相同。在垂体提取物中还检测到 α-MSH 免疫反应性物质的附加峰。这些肽与真实的 α-MSH、二乙酰化 α-MSH 和它们的亚砜形式共洗脱。这些结果首次提供了α-MSH 存在于硬骨鱼类大脑中的证据。我们的数据表明，在大脑中，免疫反应性对应于 α-MSH 的非乙酰化形式，而三种不同类型的 α-MSH 样分子（即去乙酰化、单乙酰化和二乙酰化形式）共存于垂体中。因此，在鲑鱼中，α-MSH 的 N 端丝氨酸的单乙酰化或二乙酰化仅在垂体水平发生。
