Developmental alteration of hormonal control in exocrine glands

本研究以发育中的大鼠颌下腺为研究对象，研究了外分泌细胞激素调控的变化。下颌骨腺的内部称为终小管，它由一个未成熟的分泌单位组成。末端小管有三种不同的细胞，腺泡细胞、腺泡原细胞和末端小管细胞。原腺泡细胞是腺泡细胞的前体，所有的原腺泡细胞在出生后第二周分化为腺泡细胞。末梢小管细胞是少年期颌下腺中被识别最多的细胞，但在成年期颌下腺中却不存在。在第18天，两性的末端小管细胞中首次发现了许多细胞质液泡的形成。分泌颗粒的明显减少和液泡的释放导致末端小管细胞转化为插管细胞。TUNEL（末端脱氧核苷酸转移酶介导的dutp -生物素缺口末端标记）方法在末端小管细胞中的少数细胞中显示阳性反应。阳性细胞数量增加到出生后28天。电镜显示核染色质聚集，提示出生后21天或更长时间终末小管细胞凋亡。这些结果提示细胞凋亡在大鼠出生后颌下腺生长过程中参与了颌下腺细胞的调控。雌激素受体的免疫组化研究和雌激素受体mRNA的原位杂交研究，以确定雌激素受体的定位。在这两项研究中，在末端小管细胞中发现了阳性结果，而在其他细胞中没有观察到反应。上述研究结果提示终小管细胞受雌激素的强烈调控。

This study used developmental rat submandibular gland, and studied alteration of hormonal control in exocrine cell.The endoportion of the submandibular gland is called the terminal tubule which is composed of an immature secretory unit. The terminal tubule has three different cells, the acinar cell, the proacinar cell and the terminal tubule cell. The proacinar cell is the precursor of the acinar cell, and all of the proacinar cells differentiate into the acinar cell by the second week after birth. Although the terminal tubule cell is the one which is recognized the most in the submandibular gland of the juvenile period, it does not exist in the adult submandibular gland. The formation of many cytoplasmic vacuoles were first identified in the terminal tubule cells of both sexes at day 18. The marked decrease of secretory granules and the release of vacuoles led to the transformation of the terminal tubules cells into the intercalated duct cells.The TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling) method showed positive reactions in a small number of cells in the terminal tubule cells. The number of positive cells increased until 28 days after birth. Electron microscopy revealed nuclear chromatin aggregation, suggesting apoptosis in terminal tubule cells 21 days or more after birth. These results suggest the close involvement of apoptosis in the regulation of cells constituting the submandibular gland in the postnatal growth of the rat submandibular gland.The immunohistochemical study of estrogen receptor and in situ hybridization study of estrogen receptor mRNA in order to identify the localization of estrogen receptor. In both study, a positive finding was recognized in the terminal tubule cell while no reaction was observed in another cells. The above study results have suggested that the terminal tubule cell is strongly controlled by estrogen.