去蛋氨酸/缬氨酸空肠喂饲荷瘤大鼠对肿瘤核酸及蛋白质代谢的影响

Influence of methionine/valine-depleted enteral nutrition on nucleic acids and protein metabolism in tumor-bearing rats

目的 观察去蛋氨酸 /缬氨酸空肠喂饲荷瘤鼠对肿瘤核酸及蛋白质代谢的影响。方法SD大鼠空肠造瘘 ,皮下接种Walker 2 5 6癌肉瘤 ,分A、B、C、D共 4组。分别以平衡氨基酸、去蛋氨酸、平衡氨基酸、去缬氨酸空肠喂养 6d ,注入3 H 蛋氨酸 /缬氨酸 7.4× 10 5Bq 0 .5、1、2、4h后分别测定肿瘤组织RNA、DNA及蛋白质的3 H掺入率。结果 B、D组各时点蛋白质3 H掺入率分别为 (0 .5 0 0±0 .0 2 0 ) %～ (3.6 70± 0 .110 ) %及 (1.887± 0 .0 2 0 ) %～ (3.813± 0 .0 76 ) % ,分别低于A、C组 ;B组RNA和DNA的3 H掺入率分别为 (0 .2 73± 0 .0 75 ) %及 (0 .2 31± 0 .0 5 2 ) % ,低于A组的 (0 .30 7±0 .0 73) %及 (0 .30 4± 0 .0 73) % ;C、D组核酸3 H掺入率差异无显著性 (P >0 .0 5 )。结论 去蛋氨酸 /缬氨酸空肠喂饲荷瘤鼠可抑制肿瘤蛋白质合成 ,缺乏蛋氨酸还可影响核酸的合成代谢。

Objective\ To investigate the effects of methionine/valine-depleted enteral nutrition on RNA, DNA and protein metabolism in tumor-bearing (TB) rats. Methods\ SD rats underwent catheterization of jejunostomy. A suspension of walker-256 sarcocarcinoma cells was subcutaneously inoculated. The TB rats were randomly divided in 4 groups: A、B、C and D. The TB rats received jejunostomy feedings supplemented with balanced amino acid, methionine/valine-depleted for 6 days before injection of 7.4×10 5 Bq 3H-methionine/valine. The 3H incorporation rate of the radioactivity into RNA, DNA and proteins in tumor tissues at 0.5、1、2、4 h postinjection was assessed. Results\ Incorporation of 3H into proteins in groups B and D were (0.500±0.020)% to (3.670±0.110)% and (1.887±0.020)% to (3.813±0.076)% respectively, lower than in groups A and C. Incorporation of 3H into RNA, DNA in group B were (0.273±0.075)% and (0.231±0.052)% respectively, lower than in group A ( P < 0.01 ). There was no significant difference in uptake of 3H by RNA and DNA between group D and group C ( P >0.05). Conclusions\ Protein synthesis was inhibited by methionine/valine starvation in TB rats and nucleic acids synthesis was reduced after methionine depletion.\;