Osajima A, Uezono Y, Tamura M, Kitamura K, Mutoh Y, Ueta Y, Kangawa K, Kawamura M, Eto T, Yamashita H, Izumi F, Takasugi M, Kuroiwa A
Second Department of Internal Medicine, University of Occupational and Environmental Health, School of Medicine, Kitakyushu, Japan.
Eur J Pharmacol. 1996 Nov 21;315(3):319-25. doi: 10.1016/s0014-2999(96)00557-2.
By using cultured rat mesangial cells, we compared the effects on cyclic nucleotide levels of adrenomedullin with those of the structurally related peptides, calcitonin gene-related peptide (CGRP) and amylin. Adrenomedullin potently increased cAMP levels 7-fold in a time- and concentration-dependent manner. Its EC50 was 3 x 10(-9) M. CGRP was less potent (2-fold) with an EC50 of 10(-7) M, and amylin had no effect on cAMP levels. All three peptides failed to increase cGMP levels. Treatment of cells with near maximal concentrations of adrenomedullin (10(-7) M) and CGRP (10(-6) M) had no additive effect on cAMP levels. Human adrenomedullin-(22-52)-NH2, a putative adrenomedullin receptor antagonist, inhibited the production of cAMP elicited by adrenomedullin (IC50: 7 x 10(-8) M) and CGRP (IC50: 5 x 10(-8) M). Human CGRP-(8-37), a CGRP receptor antagonist, conversely, reduced the cAMP elevation caused by these peptides with a lower potency (IC50: 10(-6) M for both peptides). This demonstrated that human adrenomedullin-(22-52)-NH2 was a more effective antagonist for adrenomedullin- and CGRP-specific receptors than human CGRP-(8-37). Results suggest that receptors sensitive to adrenomedullin are preferentially expressed in cultured rat mesangial cells. Immunohistochemical study showed almost no immunoreactive adrenomedullin and CGRP, if any, in the cells. Adrenomedullin may regulate mesangial function as either a paracrine or circulating hormone via a cAMP- but not a cGMP-dependent mechanism.
通过使用培养的大鼠系膜细胞，我们比较了肾上腺髓质素与结构相关肽降钙素基因相关肽（CGRP）和胰淀素对环核苷酸水平的影响。肾上腺髓质素以时间和浓度依赖性方式显著增加cAMP水平达7倍。其半数有效浓度（EC50）为3×10⁻⁹ M。CGRP作用较弱（2倍），EC50为10⁻⁷ M，而胰淀素对cAMP水平无影响。所有这三种肽均未增加cGMP水平。用接近最大浓度的肾上腺髓质素（10⁻⁷ M）和CGRP（10⁻⁶ M）处理细胞对cAMP水平没有叠加作用。人肾上腺髓质素-（22 - 52）-NH₂，一种假定的肾上腺髓质素受体拮抗剂，抑制肾上腺髓质素（IC50：7×10⁻⁸ M）和CGRP（IC50：5×10⁻⁸ M）引起的cAMP产生。相反，人CGRP-（8 - 37），一种CGRP受体拮抗剂，以较低的效力降低这些肽引起的cAMP升高（两种肽的IC50均为10⁻⁶ M）。这表明人肾上腺髓质素-（22 - 52）-NH₂对肾上腺髓质素和CGRP特异性受体是比人CGRP-（8 - 37）更有效的拮抗剂。结果表明，对肾上腺髓质素敏感的受体在培养的大鼠系膜细胞中优先表达。免疫组织化学研究显示细胞中几乎没有免疫反应性肾上腺髓质素和CGRP（如果有的话）。肾上腺髓质素可能通过cAMP依赖性而非cGMP依赖性机制作为旁分泌或循环激素调节系膜功能。
