Hilborn D A
J Cell Physiol. 1976 Jan;87(1):111-21. doi: 10.1002/jcp.1040870114.
The stimulation by calf serum of phosphate uptake into 3T3 cells results from a change in maximum velocity of the transport process with no change in the Michaelis constant. Only arsenate among a series of inorganic structural analogs of phosphate inhibited phosphate uptake indicating a high specificity for the process. The arsenate inhibition was competitive in nature. Papaverine, theophylline, and protaglandin E1, drugs known to maintain high intracellular levels of cAMP, had little effect on serum stimulated phosphate uptake. The phosphate uptake stimulating factor(s) in serum could be distinguised from the 3T3 cell survival and migration factors by stability characteristics, but this factor(s) could not be completely separated from a uridine uptake stimulation activity or growth promoting activity using a variety of serum fractionation procedures. Only partial stimulation of the uptake process was achieved with any one serum fraction indicating a multiplicity of serum components is probably involved in this process. Because of the rapidity of serum activation of phosphate uptake and its apparent independence of intracellular cyclic nucleotide levels, it is suggested that serum factors may stimulate phosphate uptake by inducing structural changes in the phosphate carrier system.
小牛血清对3T3细胞摄取磷酸盐的刺激作用源于转运过程最大速度的改变，而米氏常数不变。在一系列磷酸盐的无机结构类似物中，只有砷酸盐抑制磷酸盐摄取，这表明该过程具有高度特异性。砷酸盐抑制本质上是竞争性的。罂粟碱、茶碱和前列腺素E1，这些已知能维持细胞内高cAMP水平的药物，对血清刺激的磷酸盐摄取几乎没有影响。血清中刺激磷酸盐摄取的因子可通过稳定性特征与3T3细胞存活和迁移因子区分开来，但使用多种血清分级分离程序，该因子无法与尿苷摄取刺激活性或生长促进活性完全分离。任何一种血清组分仅能部分刺激摄取过程，这表明该过程可能涉及多种血清成分。由于血清激活磷酸盐摄取的速度很快，且明显独立于细胞内环核苷酸水平，因此推测血清因子可能通过诱导磷酸盐载体系统的结构变化来刺激磷酸盐摄取。
