Study Of The Somatostatin In Flatfish

Somatostatin (SS) was a hormone, which was observed in mammalian for the first time, later it could be found in numerous vertebrate. Up to now, SS had been proved to have important roles on growth, development, metabolism, and have many physiological functions in animal. In our country, the research on SS of fish was initiated not long, only a few reports on identification in fresh water could be found; as to seawater fish, the domestic information of SS is in blank at present. The somatostatin endocrine cells in Paralichtys olivaceus, Scophthalmus maximus and their larval , juvenile fish were identified with rabbit anti-somatostatin serum via the immunocytochemical method of Streptavidin-Biotin-Peroxidase Complex (SABC), and the types and function of SS-cells were focused on discussion in this paper.SS endocrine cells were only observed in the stomach and pancreatic islets of Paralichtys olivaceus. In the stomach, the SS-cells were dispersedly distributed among the gastric mucous epithelium, the bottom mucous epithelium of gastric pit and in the neck of gastric glands. The SS-cells among the mucous epithelium were usually in long shuttle and long neck bottle shapes, and the cells with round, ellipse or pear forms were mostly in the gastric glands. In the pancreas, only a few SS-cells were dispersedly located among the pancreatic islets, which were in round shapes. As to Scophthalmus maximus, SS-cells were observed in the retral esophagus and stomach. In the retral esophagus, a few SS-cells with round and long shuttle shapes were found in its epithelium. In the stomach, the SS-cells were also distributed among the gastric mucous epithelium and in the neck of gastric glands, the majority of cells were in round and long shuttle forms. On the basis of endocrine cells being differentiated into four types in the alimentary canal, all the four types of SS-cells were detected in the stomach of both Paralichtys olivaceus and Scophthalmus maximus. It is suggested that the stomach of flatfish is an important endocrine organ.In the development of Paralichtys olivaceus after embryo stage, the SS-cells were not detected in the digestive tract before 30 days; while 40 days later, they were observed in the epithelium of retral esophagus, the gastric glands and in its neck; the cells were in round shapes on the whole. In addition, some SS-cells in long shuttle shapes were in the retral esophagusial epithelium and all the four types of SS-cells existed in the stomach of 90 days old juvenile, which the type I, III and IV cells were the most.In the development of Scophthalmus maximus, the SS-cells were beingless in the alimentary canal before 24 days after embryo, and they occured in the stomach after 29 days. The majority of SS-cells were the type III and IV cells, which were dispersedly placed in the neck of gastric glands. All the four types of SS-cells have came forth in 90 days old juvenile, which numerous number belonged to the type I and IV, moderate to the type III, and the least to the type II. The amount of SS-cells in Scophthalmus maximus could not exceeded the amount in Paralichtys olivaceus, when they were in the same stage of development.If SS-cells are concerned with metamorphosis in Scophthalmus maximus, as we knew that the SS-cells occured at the beginning of its metamorphosis. And how could the SS-cells regulate the development of flatfish? All these questions need an advanced research in the future.It was the first time that SS endocrine cells were identified in larval juvenile and adult of flatfish by the immunocytochemical method of SABC, and the types and function of SS-cells were focused on discussion in this paper.