Rebuffat Piera, Macchi Carlo, Malendowicz Ludwik K, Nussdorfer Gastone G
Department of Human Anatomy and Physiology, University of Padua, I-35121 Padua, Italy.
Int J Mol Med. 2007 Oct;20(4):551-5.
Adrenomedullin (AM) is an endogenous regulatory peptide that exerts growth-promoting action in several normal and neoplastic tissues, and we investigated whether its gene expression changes during rat adrenal regeneration after enucleation and contra-lateral adrenalectomy. Regenerating adrenals were collected at day 0 (just after enucleation; control rats), 1, 3, 7, 14 and 28 after surgery. The immunocytochemical assay of PCNA (proliferating cell nuclear antigen) index confirmed that the early stages of regeneration can be divided into an initial differentiation period (from day 0 to day 3) and a subsequent high proliferative period (days 5 and 7) followed by a decrease in the proliferation activity. Real time-polymerase chain reaction (PCR) demonstrated that AM mRNA expression underwent a marked rise at day 1 of regeneration, attained a maximum level at days 3 and 5, and then declined from day 7, returning to the control value at days 14 and 28. Western blotting showed that AM protein expression was moderately elevated at day 1, was maximal between days 3 and 7, and then decreased at days 14 and 28, although remaining significant over the control value. Taken together, our findings indicate that the increase in the AM gene transcription and translation may be considered one of the early events in the enucleation-induced activation of local adrenocortical stem cells, conceivably favoring both the differentiation and proliferation stages of regeneration. The mechanism underlying this adrenocortical stem cell response does not seem to involve ACTH, because real time-PCR demonstrated that it also occurred in animals whose contralateral adrenal glands were spared, and consequently the level of circulating ACTH was in the normal range. It remains to be investigated whether the enucleation-induced relative hypoxia, ensuing from disruption of the vascular bed, and the local release of inflammatory cytokines may be involved in the up-regulation of AM gene expression in regenerating adrenal glands.
肾上腺髓质素（AM）是一种内源性调节肽，在多种正常组织和肿瘤组织中发挥促生长作用。我们研究了在大鼠肾上腺摘除并切除对侧肾上腺后再生过程中其基因表达是否发生变化。在术后第0天（摘除后即刻；对照大鼠）、1、3、7、14和28天收集再生的肾上腺。增殖细胞核抗原（PCNA）指数的免疫细胞化学检测证实，再生的早期阶段可分为初始分化期（从第0天到第3天）和随后的高增殖期（第5天和第7天），随后增殖活性下降。实时聚合酶链反应（PCR）表明，AM mRNA表达在再生第1天显著升高，在第3天和第5天达到最高水平，然后从第7天开始下降，在第14天和第28天恢复到对照值。蛋白质印迹法显示，AM蛋白表达在第1天适度升高，在第3天至第7天达到最大值，然后在第14天和第28天下降，尽管仍显著高于对照值。综上所述，我们的研究结果表明，AM基因转录和翻译的增加可能被认为是摘除诱导的局部肾上腺皮质干细胞激活的早期事件之一，可以想象这有利于再生的分化和增殖阶段。这种肾上腺皮质干细胞反应的潜在机制似乎不涉及促肾上腺皮质激素（ACTH），因为实时PCR表明，在对侧肾上腺未切除的动物中也会发生这种情况，因此循环ACTH水平在正常范围内。摘除引起的由于血管床破坏导致的相对缺氧以及炎症细胞因子的局部释放是否参与再生肾上腺中AM基因表达的上调仍有待研究。
