Ermak T H
Cell Tissue Res. 1977 Jan 5;176(1):47-55. doi: 10.1007/BF00220343.
The pyloric gland of Styela clava contains large glycogen deposits that are digested by treatment with alpha amylase and depleted by 15 days starvation. The deposits are surrounded by cytoplasmic regions containing smooth endoplasmic reticulum and mitochondria. The cells also have rough endoplasmic reticulum, Golgi cisterns, lysosomes, microvilli, cilia, and lateral infoldings of the plasma membrane. The fine structure of the pyloric cells and the position of tubules between the absorptive epithelium and general circulation suggest that the gland functions as the vertebrate liver in carbohydrate metabolism. The pyloric cells of Styela do not appear to be excretory in a "renal" sense, since there is no infolding of the basal plasmalemma and mitochondria are usually associated only with the glycogen deposits. However, a hepatic-like excretory role is consistent with current findings. In light of the phylogenic affinities of vertebrates and ascidians, it is possible that the pyloric gland is homologous to the liver.
柄海鞘的幽门腺含有大量糖原沉积物，用α淀粉酶处理后这些沉积物会被消化，饥饿15天后会耗尽。这些沉积物被含有滑面内质网和线粒体的细胞质区域所包围。细胞还具有粗面内质网、高尔基池、溶酶体、微绒毛、纤毛以及质膜的侧向褶皱。幽门细胞的精细结构以及吸收上皮和全身循环之间小管的位置表明，该腺体在碳水化合物代谢中起着类似于脊椎动物肝脏的作用。柄海鞘的幽门细胞在“肾脏”意义上似乎没有排泄功能，因为基底质膜没有褶皱，线粒体通常仅与糖原沉积物相关。然而，类似肝脏的排泄作用与目前的研究结果是一致的。鉴于脊椎动物和海鞘在系统发育上的亲缘关系，幽门腺有可能与肝脏同源。
