Effect of epidermal growth factor on growth and cytoskelton of

• Main Authors: Shiau-Jen Wen, 溫小娟
• Other Authors: Ming-Jer Tang
• Format: Others
• Language: zh-TW
• Published: 1993
• Online Access: http://ndltd.ncl.edu.tw/handle/97384863950576238206

碩士 === 國立成功大學 === 生理學研究所 === 81 === Epidermal growth factor (EGF), a 53-amino acid polypeptide, is a potent mitogen for proximal tubular cells. However, no one has successfully demonstrated that EGF accelerated proliferation of proximal tubular cells. Using primary culture of rabbit proximal tubules, we recently found that EGF induced 37% increase in cell number of cultured proximal tubule cells at day 5 approaching subconfluent stage, but did not accelerate proliferation when added at the lag phase. Since thymidine incorporation and cell cycle analysis have demonstrated that no significant change is found after EGF treatment, it clearly indicated EGF is not mitogen at this phase. On the contrary,it reduced protein contents of cultured proximal tubular cells dose-dependently.We further determined whether the decrease in protein contents was caused by cell floating, and our data confirmed the suspicion. Other growth factors or mitogens, such as TGFa, aFGF, bFGF, IGF-1, ADP and ATP,also induced cell floating in the same setting. Since we also observed that there were cell floating and morphological changes in cultured proximal tubular cells after 2-3 hr incubation of 10 ng/ml EGF, we therefore proposed that the cytoskeletal changes induced by EGF may lead to cell floating. Using immunocytochemical methods to determine whether EGF altered the appearance of actin, cytokeratin and b-tubulin, we found that EGF, at the dose of 0.1 ng/ml and up induced redistribution of actin, reorganization of cytokeratin filaments and elongation of b-tubulin. TGFa, IGF-1, and bFGF induced similar changes, but ADP did not. The underlying mechanisms are to be elucidated. Interestingly, the minimal dosage of EGF to induce cytoskeletal changes of proximal tubules lies within the physiological range of plasma concentration, suggesting that EGF play some roles in maintenance of cell morphology.