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Type: Artigo de periódico
Title: Proteasome Activity Is Altered In Skeletal Muscle Tissue Of Tumour-bearing Rats A Leucine-rich Diet.
Author: Ventrucci, G
Mello, M A R
Gomes-Marcondes, M C C
Abstract: Leucine can modulate skeletal muscle metabolism by enhancing protein synthesis and decreasing proteolysis. In this study, we investigated the effects of leucine on the ubiquitin-proteasome system in skeletal muscle of pregnant tumour-bearing rats fed a leucine-rich diet. Pregnant Wistar rats were distributed into three groups that were fed a semi-purified control diet (C, control; W, Walker tumour-bearing; P, pair-fed) and three other groups of pregnant rats fed a semi-purified leucine-rich diet (L, leucine; WL, Walker tumour-bearing; PL, pair-fed). The tumour-bearing rats were injected subcutaneously with a suspension of Walker 256 tumour cells. Protein synthesis and degradation were measured in gastrocnemius muscle; the total protein content and tissue chymotrypsin-like and alkaline phosphatase enzyme activities were also determined. Muscle protein extracts were run on SDS-PAGE to assess the expression of the myosin heavy chain (MHC), 20S alpha proteasome subunit, 19S MSSI ATPase regulator subunit and 11S alpha subunit. Although tumour growth decreased the incorporation of [3H]-Phe, the concomitant feeding of a leucine-rich diet increased the rate of protein synthesis. Muscle proteolysis in both tumour-bearing groups was increased more than in the respective control groups. Conversely, the leucine-rich diet caused less protein breakdown in the WL group than in the W group. Only the W group showed a significant reduction (71%) in the myosin content. In WL rats, the 20S proteasome content (32 kDa band) was reduced, while the expression of the 19S subunit was 3-fold less than in the W group and the 11S proteasome subunit reduced, to around 32% less than in the W group. These findings clearly indicate that leucine can stimulate protein synthesis and inhibit protein breakdown in pregnant rats, probably by modulating the activation of the ubiquitin-proteasome system during tumour growth.
Subject: Animals
Carcinoma 256, Walker
Dietary Supplements
Electrophoresis, Polyacrylamide Gel
Muscle, Skeletal
Myosin Heavy Chains
Pregnancy Complications, Neoplastic
Proteasome Endopeptidase Complex
Protein Biosynthesis
Rats, Wistar
Tumor Cells, Cultured
Citation: Endocrine-related Cancer. v. 11, n. 4, p. 887-95, 2004-Dec.
Rights: fechado
Identifier DOI: 10.1677/erc.1.00828
Date Issue: 2004
Appears in Collections:Unicamp - Artigos e Outros Documentos

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