Johnson Keven R, Olson Kenneth R
Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA.
J Exp Biol. 2009 Sep 15;212(18):2991-7. doi: 10.1242/jeb.031666.
Natriuretic peptides (NPs) and their receptors (NPRs) comprise an evolutionarily conserved signaling system with profound physiological effects on vertebrate renal and cardiovascular systems. Some NPs (ANP, BNP and VNP) are primarily of cardiac origin whereas CNP is common in the brain. In mammals, non-traditional sites of NPs synthesis, BNP in brain and CNP in atrium, appear to have complementary actions. In the present study, trout were chronically adapted to freshwater (FW) (a volume-loading, salt-depleting environment), saltwater (SW) (a volume-depleting, salt-loading environment), FW and fed a high-salt diet (FW-HSD) (a volume- and salt-loading regime) or acutely volume depleted or expanded by hemorrhage or infusion with dialyzed plasma to perturb volume homeostasis. The responses of brain and atrial BNP and CNP mRNA, pro-peptide, NPR-A and NPR-B were evaluated using quantitative PCR and western analysis. Brain pro-BNP and NPR-A was increased in FW-HSD trout and decreased in SW trout. Brain pro-CNP was largely unaffected whereas NPR-B mRNA was increased in FW-HSD trout. Atrial CNP, although produced at lower levels than other cardiac NPs, was markedly elevated in chronically (FW-HSD) and acutely volume expanded trout (dialyzed-plasma infusion) whereas decreased in hemorrhaged trout. These findings indicate that non-traditional NP synthesis sites in the trout probably complement the broad hypovolemic and hypotensive actions of traditional (cardiac) NP synthesis sites in response to volume expansion but not to plasma osmolarity. This supports the hypothesis that the piscine and mammalian NP systems are fundamentally similar and appear to protect the heart from volume overload.
利钠肽（NPs）及其受体（NPRs）构成了一个在进化上保守的信号系统，对脊椎动物的肾脏和心血管系统具有深远的生理影响。一些NPs（心房钠尿肽、脑钠肽和血管钠肽）主要起源于心脏，而C型钠尿肽在脑中常见。在哺乳动物中，NPs合成的非传统部位，即脑中的脑钠肽和心房中的C型钠尿肽，似乎具有互补作用。在本研究中，将虹鳟长期适应于淡水（FW）（容量负荷、盐消耗环境）、盐水（SW）（容量消耗、盐负荷环境）、淡水并喂食高盐饮食（FW-HSD）（容量和盐负荷状态），或通过出血或输注透析血浆使虹鳟急性容量减少或增加，以扰乱容量稳态。使用定量PCR和蛋白质免疫印迹分析评估脑和心房中脑钠肽和C型钠尿肽mRNA、前体肽、NPR-A和NPR-B的反应。在FW-HSD虹鳟中脑前体脑钠肽和NPR-A增加，而在SW虹鳟中减少。脑前体C型钠尿肽基本未受影响，而在FW-HSD虹鳟中NPR-B mRNA增加。心房C型钠尿肽虽然产生水平低于其他心脏NPs，但在长期（FW-HSD）和急性容量增加的虹鳟（透析血浆输注）中显著升高，而在出血的虹鳟中降低。这些发现表明，虹鳟中NPs合成的非传统部位可能在应对容量增加而非血浆渗透压时，补充了传统（心脏）NPs合成部位广泛的低血容量和低血压作用。这支持了鱼类和哺乳动物NP系统基本相似且似乎能保护心脏免受容量过载影响的假说。
