Laboratory of Physiology, Department of Marine Biosciences, Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa City, Chiba 277-8564, Japan.
Biochimie. 2012 Mar;94(3):637-48. doi: 10.1016/j.biochi.2011.09.015. Epub 2011 Sep 25.
Previous characterization of a native lamprey angiotensin II (LpAng II) that possesses a different sequence and function than teleost-type angiotensin II (Ang II) has raised a question as to the role of teleost-type angiotensin peptides in lampreys. In this study, teleost-type angiotensin like-peptides were identified in the buccal gland of lampreys by immunoassays and immunohistochemistry. The possible sources of angiotensin like-peptides were investigated in lampreys by manipulating their choice of host and food. Ang II immunoreactivity (irAng II) was detected in the buccal gland and plasma of feeding phase sea lampreys exposed to Atlantic cod, but was mostly absent in fasting lamprey. Qualitatively, the HPLC profiles of irAng II observed in the plasma, when present, were highly similar to those in buccal gland, implying that the buccal gland could be a source of plasma Ang II. Japanese lampreys force-fed with dogfish blood had significantly elevated concentrations of irAng II in their buccal glands when compared to unfed individuals, suggesting that feeding stimuli may have enhanced buccal gland activity. Teleost-type Ang II-containing proteins, other than angiotensinogen, are present in the buccal gland as trypsinization generated Ang II in vitro, and the HPLC profile of these irAng II was highly comparable to those naturally present in the buccal gland. [Asn(1), Val(5), Thr(9)]-Ang I that was identified in the buccal gland of Japanese lampreys has the same amino acid sequence to those previously isolated from the incubation of plasma and kidney extract, providing an alternative explanation for the previous isolation of teleost-type Ang I in lampreys. irAng I and irAng II were localized in the granule-like structures in the apical region of the secretory epithelia, suggesting that these peptides may be active components of lamphredin. The teleost-type angiotensin peptides in the buccal gland secretion suggested that these host-specific peptides could be part of the endocrine mimicry strategy used by lampreys to evade host immune responses and reduce immune-rejection.
先前对一种具有与硬骨鱼类血管紧张素 II（Ang II）不同序列和功能的本土七鳃鳗血管紧张素 II（LpAng II）的特性进行了描述，这引发了一个问题，即硬骨鱼类血管紧张素肽在七鳃鳗中的作用。在这项研究中，通过免疫测定和免疫组织化学方法在七鳃鳗的颊腺中鉴定出了硬骨鱼类血管紧张素样肽。通过操纵七鳃鳗的宿主和食物选择，研究了血管紧张素样肽的可能来源。在暴露于大西洋鳕鱼的摄食阶段海七鳃鳗的颊腺和血浆中检测到 Ang II 免疫反应性（irAng II），但在禁食七鳃鳗中大部分缺失。从质的方面来看，当存在时，在血浆中观察到的 irAng II 的 HPLC 图谱与在颊腺中观察到的高度相似，这意味着颊腺可能是血浆 Ang II 的来源。与未喂食的个体相比，用狗鲨血液强制喂食的日本七鳃鳗的颊腺中 irAng II 的浓度显著升高，这表明摄食刺激可能增强了颊腺的活性。除血管紧张素原外，在颊腺中还存在含有硬骨鱼类 Ang II 的蛋白质，在体外用胰蛋白酶消化可产生 Ang II，并且这些 irAng II 的 HPLC 图谱与在颊腺中天然存在的图谱高度相似。在日本七鳃鳗的颊腺中鉴定出的[Asn(1), Val(5), Thr(9)]-Ang I 与从血浆和肾提取物孵育中分离出的 Ang I 具有相同的氨基酸序列，为以前在七鳃鳗中分离出硬骨鱼类 Ang I 提供了另一种解释。irAng I 和 irAng II 定位于分泌上皮顶端区域的颗粒状结构中，表明这些肽可能是 lamphredin 的活性成分。颊腺分泌物中的硬骨鱼类血管紧张素肽表明，这些宿主特异性肽可能是七鳃鳗用于逃避宿主免疫反应和减少免疫排斥的内分泌模拟策略的一部分。
