Andreis Paola G, Albertin Giovanna, Conconi Maria Teresa, Carraro Gianni, Malendowicz Ludwik K, Ziolkowska Agnieszka, Nussdorfer Gastone G
Department of Human Anatomy and Physiology, Section of Anatomy, School of Medicine, University of Padua, I-35121 Padua, Italy.
Int J Mol Med. 2002 Oct;10(4):401-5.
Rat adrenomedullin (ADM) is a 50-amino acid hypotensive and vasodilating peptide, which derives from the posttranslational proteolytic cleavage of pro(p)ADM. ADM acts via at least two subtypes of receptors, named L1-receptor (L1-R) and calcitonin receptor-like receptor (CRLR). CRLR functions as a calcitonin gene-related peptide or a selective ADM receptor depending on the expression of the subtype 1 or the subtypes 2 and 3 of a family of receptor-activity-modifying proteins (RAMPs). Adrenal zona glomerulosa (ZG) is one of the main target tissues of ADM, which has been shown to exert a potent inhibitory effect on aldosterone secretion acting through ADM[22-52]-sensitive receptors. Reverse transcription (RT)-polymerase chain reaction (PCR) consistently allowed the detection of pADM mRNA in the ZG, but not zona fasciculata-reticularis (ZF/R) cells of the rat adrenal cortex. Immunocytochemistry and radioimmune assay showed a weak but sizeable expression of ADM protein in the ZG, but not inner adrenocortical layers. ZG cells expressed peptidyl-glycine alpha-amidating monooxigenase, the enzyme converting immature ADM to the mature peptide, thereby suggesting their potential ability to produce active ADM. RT-PCR demonstrated the presence in ZG, but not ZF/R cells, of the specific mRNAs of L1-R, CRLR and RAMPs (especially RAMP2). ZG cells were cultured in vitro for 24 or 48 h in the presence of ADM (10(-8) M) and/or its receptor antagonist ADM[22-52] (10(-6) M). ADM increased proliferation index and lowered apoptotic index of cultured cells, and the effects were annulled by ADM[22-52]. ADM[22-52] alone was ineffective in 24 h cultures, but moderately decreased proliferation index and raised apoptotic index in 48 h cultures. In conclusion, our study provides evidence that i) rat ZG cells express ADM and ADM receptor of L1 and CRLR/RAMP2 subtypes, which both are sensitive to ADM[22-52]; and ii) endogenous ADM system modulates in an autocrine/paracrine manner ZG growth, by stimulating cell proliferation and reducing cell apoptotic deletion.
大鼠肾上腺髓质素（ADM）是一种由50个氨基酸组成的具有降压和血管舒张作用的肽，它来源于前体（p）ADM的翻译后蛋白水解切割。ADM通过至少两种受体亚型发挥作用，即L1受体（L1-R）和降钙素受体样受体（CRLR）。根据受体活性修饰蛋白（RAMPs）家族中1型或2型和3型亚型的表达情况，CRLR可作为降钙素基因相关肽或选择性ADM受体发挥作用。肾上腺球状带（ZG）是ADM的主要靶组织之一，已证明ADM通过对醛固酮分泌起作用的[22-52]敏感受体发挥强大的抑制作用。逆转录（RT）-聚合酶链反应（PCR）始终能够在大鼠肾上腺皮质的ZG中检测到pADM mRNA，但在束状带-网状带（ZF/R）细胞中则检测不到。免疫细胞化学和放射免疫分析显示，ADM蛋白在ZG中有微弱但显著的表达，而在内层肾上腺皮质中则没有。ZG细胞表达肽基甘氨酸α-酰胺化单加氧酶，该酶可将未成熟的ADM转化为成熟肽，从而表明它们具有产生活性ADM的潜在能力。RT-PCR证明在ZG细胞中存在L1-R、CRLR和RAMPs（尤其是RAMP2）的特异性mRNA，但在ZF/R细胞中则不存在。将ZG细胞在体外分别与ADM（10^(-8) M）和/或其受体拮抗剂ADM[22-52]（10^(-6) M）一起培养24小时或48小时。ADM增加了培养细胞的增殖指数并降低了凋亡指数，而ADM[22-52]则消除了这些作用。单独使用ADM[22-52]在24小时培养中无效，但在48小时培养中适度降低了增殖指数并提高了凋亡指数。总之，我们的研究提供了以下证据：i）大鼠ZG细胞表达ADM以及L1和CRLR/RAMP2亚型的ADM受体，它们对ADM[22-52]均敏感；ii）内源性ADM系统通过刺激细胞增殖和减少细胞凋亡缺失，以自分泌/旁分泌方式调节ZG的生长。
