Walzem R L, Clifford C K, Clifford A J
J Nutr. 1983 May;113(5):1032-8. doi: 10.1093/jn/113.5.1032.
Although folic acid is known to be involved in the pathways of purine metabolism, the precise changes brought about in purine synthesis, reutilization, pool sizes, and ratios by experimental folate deficiency are not clear. Consequently, these aspects of purine metabolism were measured in hepatocytes from control and folate-deficient rats fed an amino acid diet with and without folic acid, respectively. Purine synthesis and reutilization were measured as the rates of incorporation of [U-14C]glycine and [G-3H]hypoxanthine, respectively, into the adenine and guanine pools of freshly isolated hepatocytes after a 3-hour incubation in folate-free, as well as folate- and/or thymidine-supplemented culture media. Hepatocytes from folate-deficient rats had the same rates of purine synthesis as those from control rats. Purine reutilization, purine pool sizes, and the adenine:guanine ratios were lower in hepatocytes from deficient compared with control rats. Purine synthesis was increased when folic acid or thymidine was added to the culture medium. Although hepatocytes from folate-deficient rats had a lower rate of purine reutilization compared with those from control rats, the reutilization rates did not respond to the addition of folic acid or thymidine to the culture medium. The data suggest that purine synthesis was not impaired but purine reutilization was diminished in folate deficiency. Thymidine was as effective as folic acid in stimulating purine synthesis in both control and folate-deficient hepatocytes.
虽然已知叶酸参与嘌呤代谢途径，但实验性叶酸缺乏导致嘌呤合成、再利用、库大小及比例发生的精确变化尚不清楚。因此，分别在喂食含和不含叶酸的氨基酸饮食的对照大鼠和叶酸缺乏大鼠的肝细胞中测量嘌呤代谢的这些方面。嘌呤合成和再利用分别通过在无叶酸以及补充叶酸和/或胸苷的培养基中孵育3小时后，[U-14C]甘氨酸和[G-3H]次黄嘌呤掺入新鲜分离肝细胞的腺嘌呤和鸟嘌呤库的速率来测量。叶酸缺乏大鼠的肝细胞与对照大鼠的肝细胞具有相同的嘌呤合成速率。与对照大鼠相比，缺乏组大鼠肝细胞中的嘌呤再利用、嘌呤库大小以及腺嘌呤：鸟嘌呤比例较低。当向培养基中添加叶酸或胸苷时，嘌呤合成增加。虽然与对照大鼠的肝细胞相比，叶酸缺乏大鼠的肝细胞嘌呤再利用速率较低，但再利用速率对向培养基中添加叶酸或胸苷没有反应。数据表明，叶酸缺乏时嘌呤合成未受损，但嘌呤再利用减少。在对照和叶酸缺乏的肝细胞中，胸苷在刺激嘌呤合成方面与叶酸一样有效。
