Mansour V M, Clarke I J, Smith A I
Baker Medical Research Institute, Prahran, Victoria, Australia.
Regul Pept. 1997 May 14;70(1):55-65. doi: 10.1016/s0167-0115(97)00018-9.
The pituitary intermediate lobe (IL) contains a single population of cells and has recently been shown to express endothelin (ET)-like peptides. The IL thus provides an excellent in vivo model to study regulation, function and processing of ET in an endocrine cell. The primary aims of the present study were to locate and characterize the precise molecular forms of ET in the ovine IL and determine if levels and/or processing of ET is under dopaminergic or other influences. We have developed a radioimmunoassay (RIA) that detects each form of ET and, when combined with reverse phase-HPLC (RP-HPLC), shows the ovine IL to contain predominantly the ET-1 isoform. In addition, using a specific anti-endothelin antiserum for immunohistochemistry (IHC), we localized ET-1 with alpha-melanocyte stimulating hormone (alpha-MSH) within the melanotroph. The effects of dopamine agonists, antagonists and hypothalamo-pituitary disconnection (HPD) on both tissue levels and processing of ET in the ovine IL were also examined. Normal sheep were treated chronically with haloperidol or bromocriptine to investigate the possibility of dopaminergic regulation of ET in the IL. In the haloperidol-treated group, plasma prolactin levels did not vary significantly from day 0 to day 8, but the bromocriptine treatment reduced prolactin levels (t = 9.4 P < 0.01). Neither bromocriptine nor haloperidol, however, affected tissue ET peptide levels or forms. After HPD, the HPLC profile of pooled IL showed that ET-1 levels in the IL are slightly increased with no change in molecular forms.
垂体中间叶（IL）由单一细胞群体组成，最近研究表明其能表达内皮素（ET）样肽。因此，IL为研究内分泌细胞中ET的调节、功能及加工过程提供了一个出色的体内模型。本研究的主要目的是定位并鉴定绵羊IL中ET的精确分子形式，并确定ET的水平和/或加工过程是否受多巴胺能或其他因素的影响。我们开发了一种放射免疫分析法（RIA）来检测每种ET形式，结合反相高效液相色谱法（RP-HPLC），结果显示绵羊IL中主要含有ET-1异构体。此外，我们使用一种特异性抗内皮素抗血清进行免疫组织化学（IHC），在黑素细胞刺激素细胞内将ET-1与α-黑素细胞刺激素（α-MSH）定位在一起。我们还研究了多巴胺激动剂、拮抗剂及下丘脑-垂体切断术（HPD）对绵羊IL中ET组织水平和加工过程的影响。对正常绵羊长期给予氟哌啶醇或溴隐亭，以研究IL中ET多巴胺能调节的可能性。在氟哌啶醇治疗组中，从第0天到第8天血浆催乳素水平无显著变化，但溴隐亭治疗降低了催乳素水平（t = 9.4，P < 0.01）。然而，溴隐亭和氟哌啶醇均未影响组织ET肽水平或形式。HPD后，合并IL的HPLC图谱显示IL中ET-1水平略有升高，分子形式无变化。
