The Inhibitory Effect Of Acetylcholine On Cell Proliferation Of Human Pituitary Adenoma And Its Mechanisms

Although the majority of human pituitary tumours are benign, one third would transfonn to be invasive, and an even smaller percentage (<1%) would become malignant. Many questions still remain unclear in our understanding of the underlying mechanisms responsible for both pituitary tumor initiation and progression. However, it is generally believed that pituitary tumors arise from a single differentiated cell type of somatic mutation and many factors may facilitate clonal expansion of the genetically altered cells. Under further investigations of pituitary paracrine network, it is well known that the network plays an important role in the regulation of hormone secretion communization and proliferation of anterior pitt駎ary cells. Acetylcholine (Ach) is one of the paracrine factors of anterior pituitary (AP). It has been revealed that acetycholine receptor (AchR) could be expressed on the membrane of several functional cell types in AP, and Ach can influence the 6 secretion of growth hormone, prolactin of Al?in many kinds animals through different ways. However, it has not been reported whether Ach has an effect on the regulation of proliferation, differentiation and apoptosis of cells in AP. To further investigate the modulation role of Ach is the basis of understanding the influence of Ach on the secretion of Al? which would not only facilitate thoroughly understanding the paracrme network in Al? but also have a positive influence on understanding the occurrence and development of pituitary adenomas. In these experiments, we firstly used method of iinmunohistochemistry to observe the expression of ChAT in normal human pituitary and three kinds pituitary tumors( prolactinoma, somatinoma and non-functional tumors). Secondly, MTT and 3H-TdR incorporation assay were employed to investigate the influence of Ach on the metabolism and proliferation of pituitary adenoma cells. Thirdly, the effect of Ach on the cell cycle and apoptosis of pituitary adenoma cells was studied by FCM and TUNEL respectively. And finally, laser scanning confocal system and RIA were employed to assay the influence of cytoplasm free ( [Ca2~] 3, cAMP, cGMP and protein kinase C (PKC) of pituitary adenoma cells under Ach. The main results are as follows: 1. There are ChAT inimunoreactive substances located not only in the cytoplast of three kinds of pituitary adenoma, but also in the cytoplasm of normal human pituitary cells, showing that there exists choline acetyletransferase(ChAT), a key enzyme in synthesis of Ach, in the cell of pituitary adenoma and normal human pituitary. Together with the data of Ach-R existing on the membrane of anterior pituitary cells, it indicates that Ach may have an influence on the secretion and proliferation of A? cell in a paracrine or autocrine way. 2. The results of MTF and 3H-TdR incorporation assay showed that Ach could inhibit the proliferation and DNA synthesis of three kinds of pituitary adenoma cells in a dose-dependent manner (P