C-type natriuretic peptie as a paracrine and an endocrine hormone

1.鳗鱼从淡水(FW)移植到海水(SW)后，血浆心钠素(ANP)和心室利钠肽(VNP)水平一过性升高。注射高渗液可显著提高鳗鱼血浆ANP和VNP水平，但血容量扩张对鳗鱼的促分泌剂作用较小。结论：1.提高灌流后鳗鱼心脏ANP和VNP的分泌，提示渗透调节是鳗鱼ANP和VNP分泌的主要容量调节机制，渗透刺激是由心肌细胞自身感受到的。全身放射自显影显示鳃中有致密的鳗鱼心钠素积聚。放射配基结合分析表明，大多数鳗鱼鳃中的ANP受体是清除型NPR-C；然而，只有FW鳗鱼的鳃中也存在鸟苷环化酶偶联的CNP特异性NPR-B。这与南鳗中NPR-B信息的表达要比黄鳗中表达的少得多是一致的。ANP抑制水和鳗鱼的饮水和肠道对水和钠的吸收。ANP还抑制皮质醇的分泌，皮质醇是一种对西南适应很重要的鱼类矿物皮质激素，仅在西南鳗鱼中引起抗利尿和钠尿。推测心钠素可能是西南鱼体内的一种钠挤压激素。B型利钠肽(BNP)是从牛蛙的心脏中分离得到的。因此，半水栖两栖动物的胸腔中似乎有四足类的BNP，而不是鱼型的VNP。

1. Plasma atrial and ventricular natriuretic peptide (ANP and VNP) levels increased transiently after transfer of eels from fresh water (FW) to seawater (SW). Injection of hypertonic solutions markedly increased plasma ANP and VNP levels, but blood volume expanasion was a much smaller secretagogue in the eel. ANP and VNP secretion increased in isolated, perfused eel heart after prefusate osmolality was increased These results show that osmotic requlation dominates volemic requlation for ANP and VNP secretion in the eel, and osmotic stimulus was perceived by cardiocytes themselves.2. Whole-body autoradiography revealed dense accumulation of ^<125>I-eel ANP in the gill. Radio-ligand binding assay showed that most ANP receptors in the eel gill are clearance type NPR-C ; however, guanylate cyclase-coupled, CNP-specific NPR-B was also present in the gill of only FW eels. This is consistent with much less expression of NPR-B message in SW eels than in FW eels.3. ANP inhibits drinking and intestinal absorption of water and sodium in both FW and eels. ANP also inhibits secretion of cortisol, a fish mineralocorticoid important for SW adaptation, and causes antidiuresis and natriuresis only in SW eels. It seems that ANP is a sodium extruding hormone in SW fish.4. B-type natriuretic peptide (BNP) was isolated from the cardiac ventricle of bullfrog. Thus semiaquatic amphibians seem to have terapod-type BNP not fish-type VNP in their Ventriles.