Fitatos em farelo de arroz estabilizado e seu efeito repressor sobre a absorção de chumbo pelo rato

AUTOR(ES)
DATA DE PUBLICAÇÃO

1999

RESUMO

Lead is recognized as a toxic metal in humans and exposure of the general population through food and water remains a concern of public health authorities. The absorption and distribution of lead in animals involves various chemical, physiological and nutritional factors. Among those, dietary fiber and phytic acid have been proposed to prevent lead poisoning by lowering the gastrointestinal absorption and deposition of the heavy metal. Rice bran or rice polish is a by-product that contains both, unusually large quantities of phytic acid and significant amounts of fiber. The present work describes the effect on the uptake of lead by blood, liver, kidney and bone when stabilized rice bran is added to a standard rat diet as a source of phytic acid. Diets were prepared containing two levels of fiber and four levels of phytic acid. While fiber in the diets was supplied by either micro-cristalline cellulose (C), Control, or rice bran, the source of phytate was either the full-phytate (F) or partially dephytinized bran (Fd) in diets that were either straight or contaminated with 160mg/kg of lead as PbO. Male Wistar rats (two-months old, 271 g) were used in two experiments. For experiment 1, six groups (n = 7 x 6) received: B (basal, AIN-93G, 5% cellulose fiber), BF (same as B, but containing 17% of F instead of C, to provide 5% of insoluble fiber), C5 (same as B, but contaminated), C1 (similar to C5, except that contained 1.2% of C), F5 (same as BF, but contaminated), and F1 (similar to F5, except that contained 4.7% of F, supplying 1.2% insoluble fiber). Experiment 2, consisted of three groups, (n = 7 x 3), receiving: B, F+Fd (same as F5, except that the fiber proceeded 50% from F and 50% from Fd) and Fd (same as F5, except that the fiber was supplied by Fd, only). Lead contents in tissues were determined by atomic emission spectrometry (ICP-AES). The inositol phosphate fractions in the stabilized rice bran were determinated by HPLC before and after dephytinization with exogenous phytase. Inositol hexaphosphate (phytic acid) was the major fraction found in the bran, regardless of the processes. Removal of phytate by exogenous phytase proved to be a rather inefficient process Pb accumulation in femur, liver, and kidney of the animals fed diets F5, F+Fd and Fd were significantly lower (P <0.05) than those consuming diets C5 e C1. The levels of the metal accumulated in kidney and liver showed that retention by these organs was inversely proportional to the quantity of phytate in the diet. Pb values observed in all tissues for diet F1 were significantly (P <0.05) lower than for C1. Rice bran, when used at its lowest level (4.7%), showed to be effective as a dietary protecting agent, especially in relation to cellulose. Substituting rice bran for cellulose in the diet resulted in significant additional protection to the rat against dietary lead intoxication. The data suggest that phytic acid in rice bran is a determining factor in the prevention of lead absorption by the gut.

ASSUNTO(S)

chumbo fibras farelo de arroz dietas

ACESSO AO ARTIGO

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