Zini S, Fournie-Zaluski M C, Chauvel E, Roques B P, Corvol P, Llorens-Cortes C
Institut National de la Santé et de la Recherche Médicale, Unité 36, Collège de France, Paris.
Proc Natl Acad Sci U S A. 1996 Oct 15;93(21):11968-73. doi: 10.1073/pnas.93.21.11968.
Angiotensin (Ang) II and Ang III are two peptide effectors of the brain renin-angiotensin system that participate in the control of blood pressure and increase water consumption and vasopressin release. In an attempt to delineate the respective roles of these peptides in the regulation of vasopressin secretion, their metabolic pathways and their effects on vasopressin release were identified in vivo. For this purpose, we used recently developed selective inhibitors of aminopeptidase A (APA) and aminopeptidase N (APN), two enzymes that are believed to be responsible for the N-terminal cleavage of Ang II and Ang III, respectively. Mice received [3H]Ang II intracerebroventricularly (i.c.v.) in the presence or absence of the APN inhibitor, EC33 (3-amino-4-thio-butyl sulfonate) of the APN inhibitor, EC27 (2-amino-pentan-1,5-dithiol). [3H]Ang II and [3H]Ang III levels were evaluated from hypothalamus homogenates by HPLC. EC33 increased the half-life of [3H]Ang II 2.6-fold and completely blocked the formation of [3H]Ang III, whereas EC27 increased the half-life of [3H]Ang III 2.3-fold. In addition, the effects of EC33 and EC27 on Ang-induced vasopressin release were studied in mice. Ang II was injected i.c.v. in the presence or absence of EC33, and plasma vasopressin levels were estimated by RIA. While vasopressin levels were increased 2-fold by Ang II (5 ng), EC33 inhibited Ang II-induced vasopressin release in a dose-dependent manner. In contrast, EC27 injected alone increased in a dose-dependent manner vasopressin levels. The EC27-induced vasopressin release was completely blocked by the coadministration of the Ang receptor antagonist (Sar1-Ala8) Ang II. These results demonstrate for the first time that (i) APA and APN are involved in vivo in the metabolism of brain Ang II and Ang III, respectively, and that (ii) the action of Ang II on vasopressin release depends upon the prior conversion of Ang II to Ang III. This shows that Ang III behaves as one of the main effector peptides of the brain renin-angiotensin system in the control of vasopressin release.
血管紧张素（Ang）II和Ang III是脑肾素-血管紧张素系统的两种肽类效应物，它们参与血压控制，并增加水的摄入量和血管加压素的释放。为了阐明这些肽在血管加压素分泌调节中的各自作用，在体内确定了它们的代谢途径及其对血管加压素释放的影响。为此，我们使用了最近开发的氨肽酶A（APA）和氨肽酶N（APN）的选择性抑制剂，这两种酶分别被认为负责Ang II和Ang III的N端裂解。在存在或不存在APN抑制剂EC33（3-氨基-4-硫代丁基磺酸盐）或APN抑制剂EC27（2-氨基戊烷-1,5-二硫醇）的情况下，给小鼠脑室内注射（i.c.v.）[3H]Ang II。通过高效液相色谱法（HPLC）从下丘脑匀浆中评估[3H]Ang II和[3H]Ang III的水平。EC33使[3H]Ang II的半衰期延长了2.6倍，并完全阻断了[3H]Ang III的形成，而EC27使[3H]Ang III的半衰期延长了2.3倍。此外，在小鼠中研究了EC33和EC27对Ang诱导的血管加压素释放的影响。在存在或不存在EC33的情况下，脑室内注射Ang II，通过放射免疫分析（RIA）估计血浆血管加压素水平。虽然Ang II（5 ng）使血管加压素水平增加了2倍，但EC33以剂量依赖性方式抑制Ang II诱导的血管加压素释放。相反，单独注射EC27以剂量依赖性方式增加血管加压素水平。Ang受体拮抗剂（Sar1-Ala8）Ang II的共同给药完全阻断了EC27诱导的血管加压素释放。这些结果首次证明：（i）APA和APN在体内分别参与脑Ang II和Ang III的代谢，并且（ii）Ang II对血管加压素释放的作用取决于Ang II预先转化为Ang III。这表明Ang III在控制血管加压素释放方面表现为脑肾素-血管紧张素系统的主要效应肽之一。
