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      Dietas à base de arroz e feijão aumentam a atividade plasmática e hepática da gama-glutamiltranspeptidadase em ratos jovens

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          Abstract

          O efeito de dietas à base de arroz-feijão sobre a atividade plasmática e hepática da gama-glutamiltranspeptidase-GGT foi avaliado em ratos jovens (Experimento A) e adultos (Experimento B). Os animais receberam dietas isocalóricas contendo três níveis de proteína de Arroz, Feijão, Arroz-Feijão ou Caseína, durante 28 dias. Com os menores níveis distintos de proteína dietética, a atividade plasmática e hepática da GGT mostrou-se significativamente elevada em relação ao grupo controle de Caseína a 25%, assemelhando-se àquela do grupo aprotéico. Essa elevação foi mais efetiva com dietas de Feijão e Arroz-feijão em ratos jovens, evidenciando que o efeito da restrição protéica é exacerbado pela baixa disponibilidade de aminoácidos sulfurados, além de um efeito diferencial com a idade. As alterações observadas sugerem uma adaptação metabólica da GGT aos níveis inadequados de proteína e sobretudo de aminoácidos sulfurados e subsidiam a hipótese de redução no nível de glutátion com dietas à base de leguminosas.

          Translated abstract

          Rice and bean diets increase hepatic and plasmatic activity of gammaglutamyltranspeptidase in growing rats. The effect of feeding rice and bean diets in both hepatic and plasmatic activity of gamma-glutamyltranspeptidase-(GGT-EC 2.3.2.2) activity was evaluated in growing-rats (Experiment A) and mature rats (Experiment B). During 28 days, the animals were fed with isocaloric-diets composed by tree levels of rice, bean or rice-and-bean protein. Similarly with the aproteic group, a significant increase on both the hepatic and plasmatic GGT activity were showed with the lowest leves of protein, when compared with 25% casein control group. This rise was more effective in growing-rats fed on legume-based diets (as bean or rice-and-bean diets), making evident a differential effect of age and an exacerbated effect of the protein restriction with the lowest sulfur amino acids disposal. These alterations suggest a metabolic adaptation of GGT to both the inadequate protein and sulfur-amino acid levels, thus supporting the hypothesis that the Glutathione levels may be reduced by these legume-based diets.

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          Most cited references39

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          On the enzymology of amino acid transport.

          A MEISTER (1973)
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            Synthesis of Peptides in Enzymic Reactions involving Glutathione

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              Transport of gamma-glutamyl amino acids: role of glutathione and gamma-glutamyl transpeptidase.

              This work relates to the hypothesis that one of the mechanisms that mediates amino acid translocation across cell membranes involves the action of membrane-bound gamma-glutamyl transpeptidase on intracellular glutathione and extracellular amino acids to form gamma-glutamyl amino acids. According to this idea, the latter are translocated into the cell where the gamma-glutamyl moiety is removed to yield free amino acids. Previous studies in this laboratory showed that intracellular glutathione is translocated out of many cells. We have now directly examined the transport of gamma-glutamyl amino acids into tissues in the mouse by use of the model substrate L-gamma-glutamyl-L-[14C]methionine sulfone. Of 11 tissues examined, only the kidney showed strong and preferential uptake of the substrate. A substantial amount of the administered L-gamma-glutamyl-L-[14C]methionine sulfone was found intact in the kidney; the total uptake of this compound was greater (by about 2-fold) than that of free L-methionine sulfone. Studies with a number of other gamma-glutamyl amino acids and gamma-glutamyl compounds indicate that the kidney has a relatively specific transport system for gamma-glutamyl amino acids. Small but significant amounts of gamma-glutamylmethionine sulfone were found in the liver and pancreas, suggesting that other tissues may also have this system. Transport of gamma-glutamylmethionine sulfone into the kidney was inhibited by inhibitors of glutathione synthesis and of gamma-glutamyl transpeptidase. The results suggest that both the transpeptidase and glutathione may be involved in transport of gamma-glutamyl amino acids.
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                Author and article information

                Contributors
                Role: ND
                Role: ND
                Role: ND
                Journal
                alan
                Archivos Latinoamericanos de Nutrición
                ALAN
                Sociedad Latinoamericana de Nutrición (Caracas )
                0004-0622
                December 2000
                : 50
                : 4
                : 346-352
                Affiliations
                [1 ] Universidade de São Paulo Brasil
                Article
                S0004-06222000000400005
                67748549-e2de-4cba-b2c7-fe6249159c23

                http://creativecommons.org/licenses/by/4.0/

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                SciELO Venezuela

                Self URI (journal page): http://www.scielo.org.ve/scielo.php?script=sci_serial&pid=0004-0622&lng=en
                Categories
                NUTRITION & DIETETICS

                Nutrition & Dietetics
                Gamma-glutamyltranspeptidase,protein deficiency,rice-bean diets,growing-rats,mature rats,gama-glutamiltranspeptidase,deficiência protéica,dietas de arroz-feijão,ratos jovens,ratos adultos

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