Day R, Schäfer M K, Collard M W, Weihe E, Akil H
J. A. DeSève Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montreal, Quebec, Canada.
Endocrinology. 1993 Dec;133(6):2652-9. doi: 10.1210/endo.133.6.8243288.
The distribution of prodynorphin (proDyn) messenger RNA (mRNA) was examined in the rat pituitary using Northern and in situ hybridization analysis. Anterior pituitary gonadotrophs are known to express ProDyn, but the present study demonstrated that proDyn mRNA was also expressed in the intermediate lobe melanotrophs and was colocalized with POMC mRNA. The 2.6-kilobase proDyn transcript observed in the intermediate lobe was shown to be translatable by polysome analysis. Immunohistochemical studies showed dynorphin (Dyn)-like immunoreactivity in all intermediate lobe melanotrophs. Intermediate lobe proDyn gene expression was not regulated by dopamine, in contrast to intermediate lobe POMC mRNA levels, which were increased with haloperidol and decreased with bromocriptine treatment, as expected. A gender difference in ProDyn gene expression was noted, since intermediate lobes of male rats had nearly 2-fold higher proDyn mRNA levels than intermediate lobes of female rats. In contrast, no gender difference of intermediate lobe POMC mRNA levels were detected. ProDyn mRNA levels were up-regulated by 3- to 4-fold in the intermediate lobes of postpartum females as compared to pregnant or nonpregnant female rats, whereas POMC mRNA levels were unchanged, suggesting a role for intermediate lobe ProDyn in the postpartum period of the female rat. Although our results demonstrate proDyn and POMC coexpression in the pituitary intermediate lobe melanotrophs and show a differential regulational control for each gene in this tissue, the present data also strengthen the notion that proDyn is a precursor that has a role to play in reproductive functions.
采用Northern印迹法和原位杂交分析法研究了大鼠垂体中前强啡肽原（proDyn）信使核糖核酸（mRNA）的分布情况。已知垂体前叶促性腺细胞表达ProDyn，但本研究表明，proDyn mRNA也在中间叶促黑素细胞中表达，并与阿片促黑皮质素原（POMC）mRNA共定位。通过多核糖体分析表明，在中间叶观察到的2.6千碱基的proDyn转录本是可翻译的。免疫组织化学研究显示，所有中间叶促黑素细胞中均有强啡肽（Dyn）样免疫反应性。与预期的中间叶POMC mRNA水平相反，中间叶proDyn基因表达不受多巴胺调节，POMC mRNA水平在氟哌啶醇处理后升高，在溴隐亭处理后降低。注意到ProDyn基因表达存在性别差异，因为雄性大鼠中间叶的proDyn mRNA水平比雌性大鼠中间叶高近2倍。相比之下，未检测到中间叶POMC mRNA水平存在性别差异。与怀孕或未怀孕的雌性大鼠相比，产后雌性大鼠中间叶的ProDyn mRNA水平上调了3至4倍，而POMC mRNA水平未发生变化，这表明中间叶ProDyn在雌性大鼠产后发挥作用。尽管我们的结果表明proDyn和POMC在垂体中间叶促黑素细胞中共表达，并显示了该组织中每个基因的差异调控，但目前的数据也强化了proDyn是一种在生殖功能中发挥作用的前体的观点。
