Pizzorno G, Moroson B A, Cashmore A R, Beardsley G P
Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut 06510.
Cancer Res. 1991 May 1;51(9):2291-5.
(6R)-5,10-Dideaza-5,6,7,8-tetrahydrofolic acid [(6R)DDATHF] is a folate antimetabolite with activity specifically directed against de novo purine synthesis, primarily through inhibition of glycinamide ribonucleotide transformylase. This inhibition resulted in major changes in the size of the nucleotide pools in CCRF-CEM cells. After a 4-h incubation with 1 microM (6R)DDATHF, dramatic reductions in the ATP and GTP pools were observed, with almost no effect on CTP, UTP, and deoxyribonucleotide pools. When the incubation was continued in drug-free medium, recovery of ATP and GTP pools was protracted. ATP did not return to normal until 24-36 h, and GTP pools were only partially repleted by 48 h. The ATP and GTP pools were not affected when the initial 4-h incubation with (6R)DDATHF was conducted in the presence of 100 microM hypoxanthine. Addition of hypoxanthine to the medium after a 4-h incubation with (6R)DDATHF caused rapid recovery of the ATP and GTP pools. Similar effects were seen when the purine precursor aminoimidazole carboxamide was used in place of hypoxanthine. The effect of (6R)DDATHF on nucleotide pools and the capability of hypoxanthine or aminoimidazole carboxamide to prevent or reverse this phenomenon correlated directly with the inhibition of cell growth. Presumably as a consequence of the decrease in purine nucleotide triphosphate levels, the conversion of exogenously added uridine, thymidine, and deoxyuridine to nucleotides was markedly decreased. These effects were protracted for almost 48 h and were also reversed by hypoxanthine. Differential repletion of ATP and GTP pools after (6R)DDATHF pre-treatment demonstrated that diminished precursor phosphorylation is primarily a consequence of GTP rather than ATP starvation.
(6R)-5,10-二去氮杂-5,6,7,8-四氢叶酸[(6R)DDATHF]是一种叶酸抗代谢物，其活性主要通过抑制甘氨酰胺核糖核苷酸转甲酰酶，特异性地针对嘌呤从头合成。这种抑制导致CCRF-CEM细胞中核苷酸池大小发生重大变化。用1微摩尔(6R)DDATHF孵育4小时后，观察到ATP和GTP池显著减少，而对CTP、UTP和脱氧核苷酸池几乎没有影响。当在无药物培养基中继续孵育时，ATP和GTP池的恢复过程延长。ATP直到24 - 36小时才恢复正常，GTP池在48小时时仅部分补充。当在100微摩尔次黄嘌呤存在的情况下用(6R)DDATHF进行初始4小时孵育时，ATP和GTP池不受影响。在用(6R)DDATHF孵育4小时后向培养基中添加次黄嘌呤，导致ATP和GTP池迅速恢复。当用嘌呤前体氨基咪唑甲酰胺代替次黄嘌呤时，观察到类似的效果。(6R)DDATHF对核苷酸池的影响以及次黄嘌呤或氨基咪唑甲酰胺预防或逆转这种现象的能力与细胞生长的抑制直接相关。推测由于嘌呤核苷酸三磷酸水平降低，外源添加的尿苷、胸苷和脱氧尿苷向核苷酸的转化显著减少。这些影响持续了近48小时，也被次黄嘌呤逆转。(6R)DDATHF预处理后ATP和GTP池的差异补充表明，前体磷酸化减少主要是GTP饥饿而非ATP饥饿的结果。
