Differential effects of protein restriction on gamma-glutamyltranspeptidase [EC 2.3.2.2] activity in young and mature rats

Gamma-glutamyltranspeptidase (GGT, EC 2.3.2.2) activity was determined in the plasma and liver of 40 young (50 days old) and 40 mature (300 days old) male Wistar rats, after a protein restriction period of 28 days. Casein protein levels used were: 1 percent, 3 percent, 5 percent, 7 percent and 28 percent (control). Weanling rats submitted to protein-free diet and adult rats submitted to that and other low-protein diets (1 percent, 3 percent or 5 percent casein) presented weight reductions (-0.38 +/- 0.07 g/day and -0.98 +/- 0.19 g/day, respectively). Only in young animals did these weight reductions parallel those of food consumption (37 +/- 12 percent of control), plasma protein (52 +/- 11 percent of control), plasma albumin (70 +/- 12 percent of control), hepatic RNA (68 +/- 7 percent of control) and protein (71 +/- 8 percent of control). A marked effect of the protein restriction, increasing the GGT activity, was also observed only in young rats. A significant (P<0.05) rise was promoted by the protein-free diet in the plasma GGT (2.83 +/- 1.39 vs 0.69 +/- 0.50 mU/ml for control) and by both the protein-free and 3 percent casein diets, in the liver GGT (respectively, 16.00 +/- 6.72 and 7.75 +/- 3.49 vs 0.94 +/- 0.57 U/g protein for control). The different results obtained for young in relation to mature animals could be explained by the reduction of both protein and sulfur-containing amino acid requirements with aging.

A kinetic study of some factors which influence the intestinal absorption of calcium in rats

Rats weighing 100 ñ 8 g were used in an in vivo kinetic study of the intestinal absorption of calcium (CaA) from there systems: 1) CaCl2, 2) whole cow's milk (M), and 3) a taple Brazilian diet (SBD). Food substrates were treated with HCl, neutralized and diluted with 0.15 mM NaCl to different concentrations. Each dilution was assayed by introducing 2 ml into the small intestine and the final amount of Ca*+ in the small intestine was determined 30 min later. The values for velocity (v= Vmax (Ca*+ in the small intestine was determined 30 min later. The values for velocity (v+Vmax (Ca*+)/(Ca*+) + Km) and affinity (1/Km) for the food substrates were 1.35, 15.51 and 2.31 *g Ca*+/min and 0.29, 0,016 and 0.266 *g Ca*+/ml, respectively. We conclude that the higher affinities observed for CaCl2 and SBD were not correlated with velocity. Factors modifying CaA appear to be protein (stimulator) and phylate and fiber (inhibitors)

Rice and beans: effect of milk, mineral, and vitamina A, on weight gain, food intake, and body protein retention

Ratas recién destetadas fueron alimentadas con dietas de: arroz/frijoles (RB) suplementadas o no con minerales (M); vitamina A (A); M + A (MA), o leche (L), que contenían de 3 a 14% de proteína. Según se determinó a través de diversas mediciones, los mejores reutlados se observaron en el grupo alimentado con la dieta RB suplementada con L, seguido por los grupos que recibieron las dietas MA y M. La utilización proteínica de la dieta de RB, así como el requerimiento mínimo de proteína para mantenimiento de peso corporal, depende de los nutrientes suploementarios. Puede que el mecanismo de este efecto esté relacionado con el apetito de los animales y con la ingesta energética voluntaria, la que es influencia y regulada por la composición d ela dieta

Corn amino acid imbalance and the role of leucine excess.

Se llevo a cabo un estudio en dos modelos experimentales usando ratas recien destetadas de la cepa Wistar, las que se alimentaron con dos dietas isocaloricas que contenian 7% de proteina. En la elaboracion de la dieta Modelo I se utilizaron dos variedades geneticas de maiz, maiz comun (MC) o maiz Opaco-2(M). La dieta Modelo II contenia: caseina al 7% de proteina libre de acido nicotinico, a fin de realzar las condiciones limitantes del triptofano, al igual que en la dieta MC del Modelo I. Luego se determino el balance de nitrogeno, urea urinaria y grasa hepatica.Los resultados sugirieron que el desbalance de la proteina del MC esta relacionado con las limitaciones en cuanto al contenido de lisina y triptofano, aun cuando el exceso de leucina tambien desempena un papel de importancia

Digestibilidade e eficiencia da proteina de uma mistura de arroz e feijao. / Digestibility and protein efficiency of a blend of rice and beans

A despeito de inumeros trabalhos cientificos e ainda discutivel e problematica a escolha de um metodo biologico rapido e eficiente de avaliacao do valor nutricional de proteinas.Nesta investigacao estudou-se em animais (ratos) a digestibilidade (D) de proteinas de dietas contendo arroz e feijao, ou caseina, em diferentes teores proteicos, fazendo a recuperacao com dieta de leite. O parametro "D" relacionado ao indice de limitacao aminoacidica da proteina (computo quimico "C") superestimou a qualidade proteica em relacao a outros metodos. Suplementacao de leite a 10% de proteina foi eficiente em todas as situacoes nutricionais