| The effects of extremely low frequency pulsed electromagnetic fields (ELFPEMF) have been studied in a wide variety of in vitro and in vivo systems. PC12 cells, a cell line derived from a rat adrenal pheochromocytoma, are sensitive to ELF fields and have proved a useful model system for adrenal chromaffin cells and sympathetic neurons. In this experiment, employing immunohistochemistry, HPLC analysis, western blotting and with the help of the image-ananysising softwares, the bioeffects of the f=50Hz, t =20μS, Epp= 1 V/cm ELF EMF was determined by evaluating the length of the NGF receptor clustering, outgrown neurites, TH level as well as neurotransmitter biosynthesis and release level.In our first part of the experiment, adopting the immunohistochemistry, we proved that the stimulation of ELF can lead to a NGF receptor clustering in PC12. Cells that are exposed to ELF for 15 minutes can cause the NGF receptors to cluster to a very obvious extend, .the clusters are as obvious as the NGF treated cells. While the 5 minutes and the 30 minutes groups have smaller clusters and the fluorescence are much weaker.With the help of an image-ananysising software, neurite outgrowth was tested. The results show that 3 days after the exposure, the length of the neurites do not change significantly, except the 20 minutes exposure group (P<0.01). But 4 days after the exposure, all the groups bear the neurites that are significantly longer than the control, with the 15 minutes group the longest ones. In another aspect, ELF dose not seem to have great effect on the change of the number of the neurites that one cell bear.We also investigate the effects of ELF on the biosynthesis of TH. The western blotting experiments show that shortly exposed cells can promptly be activated to express TH at a high level (187% higher than that of the control group). While within the same culture period, TH synthesis is inhibited in the long term exposed groups.On the contrary, after a longer culture period, the shortly exposed groups show inhibited TH synthesis activity, while long term exposed groups have enhanced activities. With 10,15, 20, 30 minutes group top the expression level after a culture period of 1 day, 2days, 3days and 4 days respectively. After that, we further test the signaling pathways that are involved in the ELF and NGF stimulation. The results suggest that PKA is the most important pathway that is involved in the normal TH synthesis and the ELF stimulation activity, and it also plays a role in the NGF stimulation of TH expression, while NGF can also activate some more pathways other than the PKA pathway. Ras/MEK pathway for example seem to be an important pathway in the NGF stimulation in TH biosynthesis.To determine whether ELF stimulation alters catecholamine metabolism, PC12 was exposed for varying periods of time. A time course study show a similar result as that of the western blotting experiment. Short term exposure can lead to a quick DA release, and after a prolonged culture, long term exposures provoke a significant DA release increase. The results of the inhibitor experiments indicate that PKA is the most important pathway that is involved in the realization of the bioeffect of ELF, while the NGF have a wider selection of pathways, apart from the PKA pathway, Ras/MEK is also an important related pathway.
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