Verbost P M, Butkus A, Atsma W, Willems P, Flik G, Bonga S E
Department of Animal Physiology, University of Nijmegen, Netherlands.
Mol Cell Endocrinol. 1993 May;93(1):11-6. doi: 10.1016/0303-7207(93)90133-5.
Stanniocalcin (STC) decreases branchial Ca(2+)-uptake in fish. In order to determine its bioactive domain, synthetic fragments (U amino acids (aa) 1-20; V aa 103-136; W aa 202-231) of eel STC were tested for their effect on Ca2+ uptake in tilapia (Oreochromis mossambicus). Ca2+ uptake was inhibited by an N-terminal fragment but not by a midfragment nor a C-terminal fragment of the mature hormone. We provide theoretical and experimental evidence that a midportion of STC, which is included in the synthetic fragment V, is the most antigenic site of the molecule. Polyclonal antibodies against stanniocalcin are directed against this midportion although this region of STC appears not to be essential for signal transduction. These results suggest that the currently available antibodies will recognize inactive STC fragments in the circulation. We conclude that the bioactive portion of STC does not correspond with the major antigenic portion of the hormone. The results imply that studies on plasma STC levels employing a polyclonal antiserum against STC should be interpreted with care.
鲽鱼降钙素（STC）可降低鱼类鳃对钙离子的摄取。为确定其生物活性结构域，对鳗鱼STC的合成片段（U：氨基酸（aa）1 - 20；V：aa 103 - 136；W：aa 202 - 231）进行了测试，观察其对罗非鱼（莫桑比克罗非鱼）钙离子摄取的影响。成熟激素的N端片段可抑制钙离子摄取，而中间片段和C端片段则无此作用。我们提供了理论和实验证据，表明合成片段V中包含的STC中间部分是该分子最具抗原性的位点。抗鲽鱼降钙素的多克隆抗体针对的就是这一中间部分，尽管STC的这一区域似乎对信号转导并非必不可少。这些结果表明，目前可用的抗体将识别循环中的无活性STC片段。我们得出结论，STC的生物活性部分与该激素的主要抗原部分并不对应。结果表明，采用抗STC多克隆抗血清对血浆STC水平进行的研究应谨慎解读。
