Urotensin II (U-II) was the first isopeptides characterized from the terminal organ of the urophusis and has been demonstrated to the most potent vasoconstrictor identified to date.

• 尾加压素II（urotensin II，U II）最早是从硬骨鱼脊髓尾部分离出来的神经环肽，是迄今为止所知的最强的收缩血管的活性物质。