Morphological Observation Of Cholecystokinin-, Insulinand Glucagon-secreting Cells Of Developing Pancreas In The Mouse

Objective:To observe the ontogeny, distribution, morphological characteristics of cholecystokinin immunoreactive (CCK-IR) cells, insulin immunoreactive (Ins-IR) cells and glucagon immunoreactive (Glu-IR) cells of the developing pancreas in the KM mouse. To observe whether it existed or not the coexistent phenomenon of Cholecystokinin and Insulin, Insulin and Glucagon in the same cell of the developing pancreas.Methods:The paraffin sections of KM mouse pancreas from embryonic day(ED) 11 to day 45 after birth were stained with immunohistochemical SABC method to show the ontogeny, distribution and morphological characteristics of CCK-IR cells, Ins-IR cells and Glu-IR cells. Moreover, the consecutive paraffin sections were stained with immunofluorescence double staining to observe the coexistent phenomenon of Cholecystokinin and Insulin, Insulin and Glucagon in the same cells.Results:CCK-IR cells, Ins-IR cells and Glu-IR cells existed in mouse pancreas of ED11 when the pancreas was still in the initial differentiated stage with immunohistochemical SABC method. The three kinds of cells often distributed in cluster, immunoreactivity displayed weaker, and among these positive cells were indefinite. Immunoreactivity of the three kinds of cells varied from strong to weak after ED15. The limits of these cells in the islet became clear gradually. During the advanced stage of embryonic period, the number of Ins-IR cells and Glu-IR cells which stained stronger was increased. Ins-IR cells diffused gradually in the pancreas islet, however, the distribution of Glu-IR cells varied from scattering to locating in the periphery of pancreas islet. Immunoreactivity of CCK-IR cells which displayed weaker had only seen by chance in the pancreas islet after birth.The three kinds of cells were occasionally also found in the acinar region and pancreatic duct at embryonic period. However, Ins-IR cells and Glu-IR cells could be found after birth, while CCK-IR cells did not been detected.Immunofluorescence staining revealed that CCK-IR cells were various in the shape, some cells could be seen the slender processes. The fluorescence intensity of CCK-IR cells varied from strong to weak at embryonic period; after birth, the fluorescence intensity gradually weakened. But CCK-IR cells still could be seen in the periphery of pancreas islet at day 45 after birth. The shape of Ins-IR cells and Glu-IR cells predominated in round and oval. Before ED15, the fluorescence intensity of Ins-IR cells and Glu-IR cells were weaker, furthermore, the fluorescence intensity of Glu-IR cells were much stronger than Ins-IR cells. The fluorescence intensity of both gradually strengthened from the late stage of embryonic period to day 45 after birth. Immunofluorescence double staining revealed that CCK-Ins-IR cell could be seen in the mouse pancreas all the time from ED14 to day 45 after birth. The number of CCK-Ins-IR cells predominated in the advanced stage of embryonic period and day 30 after birth. The coexistent phenomenon of Insulin and Glucagon in the same cells of the pancreas in the mouse were found from ED11 to day 45 after birth, the number of Ins-Glu-IR cells showed a peak at ED11 and day 30 after birth. Ins-Glu-IR cells were occasionally found in exocrine portion of pancreas after birth.Conclusion:1. Immunofluorescence staining was more sensible than general immunohistochemical method for detecting of CCK-IR cells of the developing pancreas.2. CCK-IR cells of the developing pancreas in the mouse had the morphological characteristics of paracrine cell; the distributional characteristics of CCK-IR cells in the developing pancreas indicate that CCK-IR cells might influence the genesis and development of endocrine cells in islet and pancreatic exocrine by endocrine and paracrine, moreover CCK-IR cells might participate in regulating secretion of pancreas in the mouse after birth.3. Immunofluorescence double staining had better manifest the coexistent phenomenon of two hormones in the same cells. In the current study we found CCK-Ins-IR cells and Ins-Glu-IR cells, which might be the primitive endocrine cells in the pancreas.4. A lot of Ins-Glu-IR cells in pancreas islet at day 30 after birth suggested thatβcells still should have the potency of division growth of pancreas islet in the mature mouse.