牙鲆生长抑素分泌细胞的免疫细胞化学研究

Immunocytochemistry study on somatostatin secreting cells in Paralichtys olivaceus

采用链霉亲合素-生物素-过氧化物酶复合物(SABC)免疫细胞化学染色技术,利用兔抗哺乳动物生长抑素血清对牙鲆(Paralichthys olivaceus)消化道(包括食道、胃、幽门垂、肠道全长及肛门)、肝胰脏、肾脏、脾脏以及生殖腺等器官的生长抑素(SS)分泌细胞进行定位和鉴别。结果表明,生长抑素分泌细胞仅存在于胃和胰岛中,其他检测部位均未见分布。在胃中,生长抑素分泌细胞主要散在分布于胃黏膜上皮、胃小凹底部上皮和胃腺的颈部周围。在胃的不同部位,生长抑素分泌细胞的分布密度存有差异,以胃体部数量最多,贲门部次之,幽门部最少。参照消化道内分泌细胞与胃肠腔或腺腔有无直接联系,以及基部有无胞质突起的分类方法,将SS分泌细胞分为4种不同的类型,这4种类型的SS分泌细胞在胃中均有出现,且不同部位出现的几率不同。其中,贲门部以第Ⅲ、Ⅰ型居多;胃体部以第Ⅳ、Ⅰ型细胞为主;幽门部仅有第Ⅰ、Ⅱ型细胞。提示,牙鲆的胃是一个复杂的内分泌器官。在胰脏中,生长抑素分泌细胞零散地分布于胰岛细胞之间,数量很少。

Somatostatin （SS） was originally isolated from ovine hypothalamus and found to inhibit the release of growth hormone（GH） from the rat pituitary. SS is now well established to be a multifunctional peptide widely distributed throughout the central nervous system and peripheral tissues, playing vast physiological roles in neuromodulation and affecting various aspects of growth,development and metabolism in vertebrates. In the present study, Paraffin slices of whole digestive tract （ including esophagus, stomach, pyloric cecum,whole intestine and anus）, liver-pancreas, kidney, spleen and gonad of Paralichtys olivaceus were prepared,and somatostatin （SS） secreting cells were identified and located using rabbit anti-mammalian SS serum with SABC immunocytochemical method. The results show that SS secreting cells are only distributed in stomach and pancreatic islets. In stomach, SS secreting cells are dispersedly distributed among the epithelium of gastric mucous membrane, the bottom of gastric pits and around the neck of gastric glands. Densities of SS secreting cells in different area of stomach varied, which is the highest in the zone of fundus and proximal two thirds of the stomach, the moderate is in the cardia area, and the smallest is in the pylorus region. According to classifying method of endocrine cells on the basis of cytoplasmic protuberance at their bottom, four types of SS secreting cells can be distinguished in the stomach, and the odds presenting in various zone of stomach is also varied. Types Ⅲ and Ⅰ are dominating SS cells in the cardia, types Ⅳ and Ⅰ are preponderant in the fundus, and types Ⅰ and Ⅱ are characteristic in the pylorus. It suggests that stomach of P. olivaceus is an important endocrine organ. In pancreas, SS secreting cells are scattered and dispersedly located in pancreatic islets. SS aroses from a multigene family. In mammals, SS exists as two biologically active forms, SS-14 and its NH2-terminal extension of 14 amino acids, SS-28. Both SS-14 and SS28 are encoded by a common gene and processed in a tissue-specific way from a single precursor, preprosomatostatin Ⅰ （pss Ⅰ ）. SS14 has been identified with the same amino acid sequence in all vertebrate species, Besides PSS Ⅰ, teleosts possess a second SS precursor （PSS Ⅱ ）, producing a second somatostatin with 22- 28 amino acid residues. Because of PSS Ⅰ and PSS Ⅱ sharing low amino acid identity, the peptide derived from preprosomatostatin Ⅱ would not be detected by only anti-mammalian SS serum used. [Journal of Fishery Sciences of China, 2007,14 （3） ： 397 - 402 ]