Influence of methionine/valine-depleted enteral nutrition on nucleic acid and protein metabolism in tumor-bearing rats.
OBJECTIVE
To investigate the effects of methionine/valine-depleted enteral nutrition (EN) on RNA, DNA and protein metabolism in tumor-bearing (TB) rats.


METHODS
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.


RESULTS
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).


CONCLUSIONS
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.
He
Yin-Cheng
YC
Department of general surgery, Zhongnan Hospital, Wuhan University, Wuhan 430071, China. w030508h@public.wh.hb.cn
Cao
Jun
J
Chen
Ji-Wei
JW
Pan
Ding-Yu
DY
Zhou
Ya-Kui
YK
D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D002279:Carcinoma 256, Walker / Q000235:genetics / Q000503:physiopathology* / Q000628:therapy; D004750:Enteral Nutrition; D005769:Gastrointestinal Motility / Q000502:physiology; D066298:In Vitro Techniques; D007583:Jejunum; D008715:Methionine / Q000172:deficiency*; D009119:Muscle Contraction / Q000502:physiology*; D009130:Muscle, Smooth / Q000503:physiopathology; D014176:Protein Biosynthesis; D011865:Radioisotope Dilution Technique; D051381:Rats; D017207:Rats, Sprague-Dawley; D013270:Stomach / Q000503:physiopathology*; D014316:Tritium; D014633:Valine / Q000172:deficiency*
D000596:Amino Acids; D014316:Tritium; D008715:Methionine; D014633:Valine