Wolfe R A, Wu R, Sato G H
Proc Natl Acad Sci U S A. 1980 May;77(5):2735-9. doi: 10.1073/pnas.77.5.2735.
125I-Labeled epidermal growth factor (EGF) binds to HeLa cells in culture under completely defined conditions in a specific and saturable manner. When the cultures are maintained in serum, all the reported phenomena of down-regulation occur. In contrast, in cultures maintained in serum-free hormone-supplemented medium, binding is maximal after 50 min and remains constant for at least 18 hr. EGF retains its mitogenic activity in this defined system; as little as 4 pM EGF elicits a 2-fold increase in cell number in 5 days. EGF appears to be in reversible equilibrium with a constant number of surface receptors, and gel filtration analysis indicates a decrease in the rate of degradation and release of bound 125I-labeled EGF. These results indicate that EGF can retain its mitogenic activity in the absence of concomitant down-regulation.
125I标记的表皮生长因子(EGF)在完全限定的条件下以特异性和可饱和的方式与培养中的HeLa细胞结合。当培养物在血清中维持时,所有报道的下调现象都会发生。相反,在无血清激素补充培养基中维持的培养物中,结合在50分钟后达到最大值,并至少保持18小时恒定。EGF在这个限定系统中保留其促有丝分裂活性;低至4 pM的EGF在5天内可使细胞数量增加2倍。EGF似乎与恒定数量的表面受体处于可逆平衡,凝胶过滤分析表明结合的125I标记的EGF的降解和释放速率降低。这些结果表明,EGF在没有伴随下调的情况下可以保留其促有丝分裂活性。