| Gonadotropin-releasing hormone (GnRH) is a decapeptide synthesized by hypothalamus and released from nerve terminals in pulsatile manner into the hypophysial-portal circulation and stimulates gonadotropin target cells in anterior pituitary. The gonadotropin response to GnRH stimulation is manifested by releasing the gonadotropins, luteinizing hormone (LH) and follicle stimulating hormone (FSH) that play a central role in control of reproduction. Recently, GnRH and its receptor have been found exist in many extra-hypothalamus and extra-pituitary tissuses, such as immune system ( T and B lymphocytes ) and gonad (ovary, oviduct, prostate, testis, placenta, et al). They are not only expressed in normal tissues, but also widely exist in various carcinoma that derived from reproductive (ovary cancer, prostate cancer) or non-reproductive tissues (breast cancer, lung cancer, pancreas cancer and hepatocellular carcinoma, et al). These indicate that they may have certain functions in regulating the growth of these neoplastic tissues.Our previous studies found that GnRH and its receptor coexisted in digestive system (such as gastric-intesinal and pancreas), and meanwhile, we found their mRNA are also present in the same organs mentioned above. We have demonstrated that cDNA sequence of GnRH receptor in submaxillarywas identical to the relative cDNA sequence of GnRH receptor in pituitary. The suppressive effect of alarelin, a kind of GnRH analogue, on the secretion of never growth factor (NGF) in submaxillary showed that these organs are the targets of GnRH. By now, there still have been no reports concerning the expression and function of GnRH and its receptor in cultured stomach smooth muscle cells (SSMC) and parietal cells of rats. Based on our previous studies, we conducted the following experiments to further clarify the following uncertainty: [1] By using immunohistochemistry and in situ hybridization, we detected the expression of GnRH receptor in cultured SSMCs of rats that we established as a new model for isolation and primary culture in vitro. [2] Radioimmuoassay was used to study the effects of GnRH analogue on PKC activity in cultured rat SSMCs. We also study the mechanism of GnRH agalogue on [Ca24]; mobilization in (SSMC) of rats by using laser confocal scanning microscope. [3] By using MTT test, 3H-TdR incorporation, average fluorescent values of proliferating cell nuclear antigen (PCNA) and flow cytometric DNA analysis, we detected effects of GnRH analogue on the proliferation of cultured SSMCs of rats. [4] The morphological methods were also used in examining the expression of GnRH and its_receptor in cultured parietal cells of rats. The GnRH sequence in cultured parietal cells of rats was analysed. [5] In order to study the possible mechanism of GnRH receptor mediated intraellular message transduction in cultured parietal cells of rats, the influence of GnRH analogue on the concentration of intracellular free calcium ion was determined by laser confocal scanning microscope.The main results were as follows:1. Stomach smooth muscle cells of rats showed GnRH receptor immunoreactivity, positive staining was located in cytoplasm rather than in nuclei. GnRH receptor was the products of the SSMCs of rats and the SSMCs also are targets of GnRH.2. By using Radioimmuoassay, we studied the effect of GnRH analogue on PKC activity in cultured rat SSMCs. The results show that alarelin could induce activation of PKC, which act in time-course manner, and the peak time of PKC activity was 3 minutes. When Alarelin was lO^lO^lO'^lO^lO'5 mol/L respectively, the PKC activity was increased gradually, and acted in dose-dependent way. It was also observed that the alarelin-stimulated activity was dependent on the presence of extracellular calcium. These results indicate that GnRH analogue can increase the PKC activity and PKC is an important signal molecule in GnRH regulating cultured stomach smooth muscle cells.3. Alarelin can elevate intracellular [Ca24] and act in dose-dependent way in SSMCs. Our...
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