Steinberg S E, Fonda S, Campbell C L, Hillman R S
Br J Haematol. 1983 Aug;54(4):605-12. doi: 10.1111/j.1365-2141.1983.tb02140.x.
To trace the development of folate-deficient abnormalities of morphology and DNA synthesis, Friend erythroleukaemia cells were grown in media containing 10(2), 10(3) and 10(4) ng of [3H]PteGlu1/ml and then transferred to folate-free media. Parameters examined were: intracellular folate levels; growth potential; morphology; dU suppression; and DNA content by flow microfluorimetry. The most sensitive indicators of folate-deficient cell growth were those related to DNA synthesis (dU and flow microfluorimetry). These became abnormal at intracellular folate levels of 0.2-0.5 ng/10(6) cells and markedly so below 0.1 ng/10(6) cells. Morphological criteria were less sensitive. Cells became megaloblastic at intracellular folate levels below 0.06 ng/10(6). The capacity of the cells to replicate in folate-free media was a function of the intracellular folate (ICF): duplications = 4.01 + ln(ICF)/0.67 (r = 0.993, P less than 0.001). These studies demonstrate that regardless of initial intracellular folate levels, cellular stigmata of folate deficiency appear when cellular folate falls below 3 X 10(5) molecules per cell (dU and flow microfluorimetry) and cells lose the capacity for further replication below 7-10 X 10(5) molecules. The intracellular folate level not only predicts early defects, but also determines the replicative capacity.
为追踪叶酸缺乏时形态学和DNA合成异常的发展过程，将Friend红白血病细胞在含有10²、10³和10⁴ ng [³H]蝶酰谷氨酸/ml的培养基中培养，然后转移至无叶酸培养基中。检测的参数包括：细胞内叶酸水平；生长潜能；形态学；dU抑制；以及通过流式细胞荧光测定法检测DNA含量。叶酸缺乏时细胞生长最敏感的指标是与DNA合成相关的指标（dU和流式细胞荧光测定法）。这些指标在细胞内叶酸水平为0.2 - 0.5 ng/10⁶细胞时出现异常，在低于0.1 ng/10⁶细胞时明显异常。形态学标准则不太敏感。细胞内叶酸水平低于0.06 ng/10⁶时会变成巨幼细胞。细胞在无叶酸培养基中复制的能力是细胞内叶酸（ICF）的函数：复制次数 = 4.01 + ln(ICF)/0.67（r = 0.993，P < 0.001）。这些研究表明，无论初始细胞内叶酸水平如何，当细胞内叶酸降至低于每细胞3×10⁵个分子时（dU和流式细胞荧光测定法）会出现叶酸缺乏的细胞特征，而当低于7 - 10×10⁵个分子时细胞失去进一步复制的能力。细胞内叶酸水平不仅能预测早期缺陷，还能决定复制能力。
