He Yin-Cheng, Cao Jun, Chen Ji-Wei, Pan Ding-Yu, Zhou Ya-Kui
Department of general surgery, Zhongnan Hospital, Wuhan University, Wuhan 430071, China.
World J Gastroenterol. 2003 Apr;9(4):771-4. doi: 10.3748/wjg.v9.i4.771.
To investigate the effects of methionine/valine-depleted enteral nutrition (EN) on RNA, DNA and protein metabolism in tumor-bearing (TB) rats.
Sprague-Dawlley (SD) rats underwent jejunostomy for nutritional support. A suspension of Walker-256 carcinosarcoma cells was subcutaneously inoculated. 48 TB rats were randomly divided in 4 groups: A, B, C and D. The TB rats had respectively received jejunal feedings supplemented with balanced amino acids, methionine-depleted, balanced amino acids and valine-depleted for 6 days before injection of 740 KBq (3)H- methionine/valine via jejunum. The (3)H incorporation rate of the radioactivity into RNA, DNA and proteins in tumor tissues at 0.5, 1, 2, 4 h postinjection of tracers was assessed with liquid scintillation counter.
Incorporation of (3)H into proteins in groups B and D was (0.500+/-0.020) % to (3.670+/-0.110) % and (0.708+/-0.019) % to (3.813+/-0.076) % respectively, lower than in groups A ((0.659+/-0.055) % to (4.492+/-0.108) %) and C ((0.805+/-0.098) % to (4.180+/-0.018) %). Incorporation of (3)H into RNA, DNA in group B was (0.237+/-0.075) % and (0.231+/-0.052) % respectively, lower than in group A (P<0.01). There was no significant difference in uptake of (3)H by RNA and DNA between group C and D (P>0.05).
Protein synthesis was inhibited by methionine/valine starvation in TB rats and nucleic acid synthesis was reduced after methionine depletion, thus resulting in suppression of tumor growth.
研究蛋氨酸/缬氨酸缺乏的肠内营养（EN）对荷瘤（TB）大鼠RNA、DNA和蛋白质代谢的影响。
对Sprague-Dawley（SD）大鼠行空肠造口术以提供营养支持。皮下接种Walker-256癌肉瘤细胞悬液。48只TB大鼠随机分为4组：A组、B组、C组和D组。在经空肠注射740KBq的（3）H-蛋氨酸/缬氨酸前，TB大鼠分别接受补充平衡氨基酸、缺乏蛋氨酸的平衡氨基酸、平衡氨基酸和缺乏缬氨酸的空肠喂养6天。注射示踪剂后0.5、1、2、4小时，用液体闪烁计数器评估肿瘤组织中放射性物质（3）H掺入RNA、DNA和蛋白质的速率。
B组和D组中（3）H掺入蛋白质的比例分别为（0.500±0.020）%至（3.67±0.110）%和（0.708±0.019）%至（3.813±0.076）%，低于A组（（0.659±0.055）%至（4.492±0.108）%）和C组（（0.805±0.098）%至（4.180±0.018）%）。B组中（3）H掺入RNA、DNA的比例分别为（0.237±0.075）%和（0.231±0.052）%，低于A组（P<0.01）。C组和D组之间RNA和DNA对（3）H的摄取无显著差异（P>0.05）。
蛋氨酸/缬氨酸饥饿抑制了TB大鼠的蛋白质合成，蛋氨酸缺乏后核酸合成减少，从而导致肿瘤生长受到抑制。
