| Objective: To observe the effects of GH releasing peptide-6 (GHRP-6) on GH secretion of human pituitary somatotrophinoma cells in vitro,and to investigate the regulatory effects of multiple intracellular "second messengers" on GH secretion by human pituitary somatotrophinomas.Materials and Methods: The response to GHRP-6, GH-releasing hormone(GHRH) and somatostatin(SS) in 6 somatotrophinomas and 3 embryo pituitaries in vitro were observed..Results:In vitro cell culture, a stimulatory response to GHRP-6 was found in both groups of somatotrophinomas, and excitative effects is not as more sensitive as normal pituitary. Howerer, the GH response time to repeated administration of GHRP-6 to somatotrophinomas was prolonged. The GH-secreting effects of GHRH or SS was only obtained in parts of somatotrophinomas. Moreover, SS only attenuation but abolished GH response to GHRP-6.Conclusion: In vitro cell culture, human pituitary cells have the same form and size, they grow dispersed and suspended, and not easy to adherence. On the contrary the abnomal human pituitary cells have different form and size, the attached cells were longer and shaped ellipse or shuttle and grown like a round or a flat under microscopy, they grow clumpy and desintegrate vigorous. The abnomal cells have parapodium and grow suspended partly, the adherence time of them is more than 24 hours, all of this increase the difficulty of cell culture. So, the success of cell culture is the compact base of studying the pituitary somatotrophinoma molecular biology. In vitro cell culture, the GH-secreting excitative effect of GHRP-6 to somatotrophinomas was not as far more sensitive as normal pituitary ,So GH-secreting pituitary adenomas manifestated autocrine characteristics. The abnormal response to repeated administration of GHRP-6 in vitro showed that the lack of desensition--negative feedback loops of GH releasing hormone receptors was associated with tumorigenesis of GH secreting adenomas. |
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