Neugut A I, Weinstein I B
In Vitro. 1979 May;15(5):363-7. doi: 10.1007/BF02616143.
The role of folate metabolism in growth control in monolayer and suspension cell cultures was studied in three related cell lines: BHK-21, polyoma-transformed BHK-21 (PyBHK), and an aminopterin-resistant derivative of BHK-21 (A5). BHK-21 cells had extremely low levels of dihydrofolate reductase, PyBHK had higher levels, and A5 had extremely high levels. Hypoxanthine and thymidine together, but not individually, induced BHK-21 to grow in agar, and stimulated its growth in agarose and monolayer culture. PyBHK and A5 grew spontaneously in agar, and hypoxanthine plus thymidine had little or no effect on their growth either in suspension or in monolayer cultures. We found that exogenous folinic acid, a derivative of folate metabolism that bypasses the function of dihydrofolate reductase, mimicked the growth-stimulatory effects of exogenous hypoxanthine plus thymidine BHK-21. We conclude that the growth limitation of BHK-21 in suspension culture is due, in part, to a deficiency of dihydrofolate reductase. This enzyme deficiency limits nucleoside synthesis and can be overcome by supplying end products of this pathway.
BHK-21、多瘤病毒转化的BHK-21（PyBHK）以及BHK-21的氨基蝶呤抗性衍生物（A5）。BHK-21细胞的二氢叶酸还原酶水平极低，PyBHK的水平较高，而A5的水平极高。次黄嘌呤和胸腺嘧啶核苷共同作用（而非单独作用）可诱导BHK-21在琼脂中生长，并刺激其在琼脂糖和单层培养物中的生长。PyBHK和A5可在琼脂中自发生长，次黄嘌呤加胸腺嘧啶核苷对它们在悬浮培养或单层培养中的生长几乎没有影响。我们发现，外源性亚叶酸（一种绕过二氢叶酸还原酶功能的叶酸代谢衍生物）模拟了外源性次黄嘌呤加胸腺嘧啶核苷对BHK-21的生长刺激作用。我们得出结论，BHK-21在悬浮培养中的生长限制部分归因于二氢叶酸还原酶的缺乏。这种酶缺乏限制了核苷合成，而通过提供该途径的终产物可以克服这一限制。
