Ginty D D, Osborne D L, Seidel E R
Department of Physiology, School of Medicine, East Carolina University, Greenville, North Carolina 27858.
Am J Physiol. 1989 Jul;257(1 Pt 1):G145-50. doi: 10.1152/ajpgi.1989.257.1.G145.
Experiments were designed to examine the effects of exogenously supplied putrescine on the synthesis of DNA, RNA, and protein in cultured epithelial cells (IEC-6). Putrescine increased aphidicolin-sensitive DNA synthesis at concentrations as low as 0.3 microM putrescine with maximal stimulation (267% control) at 10 microM. This response appeared to be an effect of increases in the intracellular concentration of putrescine as the intracellular levels of spermidine and spermine did not change over the time period examined. Furthermore, pulse-chase experiments revealed that putrescine that entered the cell was not metabolized to another polyamine or degraded. In addition, 10 microM putrescine enhanced both cycloheximide-sensitive lysine incorporation and actinomycin D-sensitive uridine incorporation, indexes of protein and RNA synthesis, respectively. Incorporation of both lysine and uridine was maximal 12 h after the addition of putrescine, whereas thymidine incorporation was still increasing at 24 h, the longest time point examined. These data suggest that putrescine synthesis and/or transport during mucosal proliferation is directly involved in the stimulation of epithelial DNA, RNA, and protein synthesis.
设计实验以研究外源添加的腐胺对培养的上皮细胞（IEC-6）中DNA、RNA和蛋白质合成的影响。腐胺在低至0.3微摩尔浓度时即可增加对阿非科林敏感的DNA合成，在10微摩尔时刺激作用最大（为对照的267%）。这种反应似乎是细胞内腐胺浓度增加的结果，因为在所研究的时间段内，亚精胺和精胺的细胞内水平没有变化。此外，脉冲追踪实验表明，进入细胞的腐胺不会代谢为其他多胺或被降解。另外，10微摩尔的腐胺分别增强了对放线菌酮敏感的赖氨酸掺入和对放线菌素D敏感的尿苷掺入，这分别是蛋白质和RNA合成的指标。赖氨酸和尿苷的掺入在添加腐胺后12小时达到最大，而胸苷掺入在24小时（所检测的最长时间点）仍在增加。这些数据表明，黏膜增殖过程中的腐胺合成和/或转运直接参与刺激上皮细胞的DNA、RNA和蛋白质合成。
