Intestinal absorption of D-galactose and L-leucine and intestinal disaccharidase activities in growing chickens fed different raw legume diets

Tannic acid inhibition of amino acid and sugar absorption by mouse and vole intestine: Tests following acute and subchronic exposure

The acute effects of tannin (tannic acid; TA) on nutrient absorption were studied by measuring sugar and amino acid uptake across the brash border (luminal membrane) of intact intestine in the presence and absence of TA. Incubation of tissue for 4-9 min in TA solution (1 mg/ml) caused a reduction in passive influx ofL-glucose in voles and mice and a reduction in carrier-mediated influx ofD-glucose and total influx ofL-proline in mice, but not voles. In subchronic experiments, mice and voles were fed for 7-14 days a diet with 4% TA, but there was no significant effect on intestinal brush border uptake ofL-glucose,D-glucose, orL-proline (or three other amino acids tested in voles). In a synthesis of our study with others in the literature, three inferences are made from the patterns of effects across solutes, time scales of exposure, and species. First, the transport inhibitory effects following acute exposure are probably mediated by two processes: increased resistance to passive flux across an effective unstirred layer juxtaposed to the brush border membrane, perhaps due to tannin-mucin binding, and reduced Na(+)-coupled nutrient uptake across the intestinal brush border. Second, there is a species sensitivity difference in TA's effect on the second process. Third, the negative effects observed at the acute time scale in vitro do not necessarily occur in animals eating TA subchronically because little TA reaches the luminal membrane, or if it does its effects are quickly reversed when the tissue is removed and washed with solution free of TA.

Influence of dietary tannic acid and polyethylene glycol on growth and intestinal D-xylose absorption of broiler cockerels and activity of serum enzymes

1. In an experiment on broiler cockerels, the influence of tannic acid (TA) and polyethylene glycol (PEG) on body weight gain (BWG), feed conversion ratio (FCR), weight of intestine and liver, the activities of serum enzymes LDH, AST, ALT and intestinal absorption function were investigated. 2. Broiler cockerels were given either a commercial diet alone (control group) or a commercial diet with TA (20 g/kg), PEG (10 g/kg) or TA plus PEG (20 + 10 g/kg), for 10 d. 3. On the last day of the experiment, all birds and remaining feed were weighed individually and a sample of blood was taken to measure the serum activities of lactate dehydrogenase (LDH), aspartate aminotransferase (AST) and alanine aminotransferase (ALT). The capacity of intestinal cells for the absorption of D-xylose was measured. Finally all birds were killed humanely and the intestine and liver were weighed. 4. The results showed that TA significantly reduced BWG and FCR, as well as the activity of LDH, AST and ALT. 5. TA also increased the relative weight of the intestine. Adding PEG alone had no effect on any of the measured parameters. 6. However, PEG improved significantly BWG, FCR and the activity of LDH and AST of TA-fed birds. 7. The plasma D-xylose concentration of experimental birds was similar for all dietary treatments most likely because of temporal separation between feeding the dietary TA and administering the D-xylose. 8. It was concluded that the presence of tannins in the GI lumen of the bird was necessary to affect the processes involved in the absorption of simple sugars such as D-xylose, at the level of intestinal absorptive cells.

Effects of faba bean tannins on the growth and histological structure of the intestinal tract and liver of chicks and rats

1. Diets containing a freeze-dried tannin extract from faba beans (Vicia faba L.) at concentrations of 0, 8 and 16 g/kg were fed to growing chicks and rats. 2. Chicks fed on the tannin-containing diets exhibited a high mortality and significant decreases in body-weight as well as lower food intakes and higher food intake:weight gain ratios (P < 0.01). In rats there was no mortality but the growth and food intake were adversely affected (P < 0.05). 3. Histological changes occurred in the ileal mucosa of chicks. Atrophy and shortening of villi with distortion of their architecture were observed. Similar histological disorders but less pronounced were also found in rats. 4. Histopathology of the liver of both chicks and rats showed an hydropic degeneration of hepatocytes, clearly more severe in the former than in the latter.

Exposure of the rat small intestine to raw kidney beans results in reorganization of absorptive cell microvilli

BACKGROUND/AIMS

A single exposure to raw kidney beans (RKB) results in vesiculation, shortening, and then regrowth of microvilli in the rat small intestine. This study investigated changes that occur in the structure of microvilli 2-10 hours after RKB exposure.

METHODS

Circumferences of microvilli from absorptive cells obtained sequentially after challenge with RKB or chow were assigned to one of three groups: small, intermediate, or large. The distribution and concentration of actin in intact mucosae or isolated epithelial sheets were determined by confocal laser scanning microscopy, immunocytochemistry, and immunoblot analysis with specific probes.

RESULTS

Six hours after exposure to RKB, most microvilli were large, abnormal in shape, and contained significantly more actin filaments than large microvilli from control rats. In addition, the fluorescence intensity of F-actin increased within injured microvilli without changes in the total intracellular actin concentration. By 8-10 hours after challenge with RKB, some microvilli remained larger than those of control rats but had resumed their normal shape and contained fewer actin filaments than at 6 hours.

CONCLUSIONS

Exposure of the rat small intestine to RKB results in enlargement of absorptive cell microvilli and reorganization of membrane and core actin filaments without changes in intracellular actin concentration. Enlarged microvilli are rapidly repaired.

Feeding differently processed soya bean. Part 2. An assessment of haematological responses in the chicken

The use of differently processed soya bean as a major source of dietary protein was evaluated in a haematological study using broiler chickens in which groundnut cake (GNC), raw soya bean (RSB), roasted soya bean (RtSB), cooked soya bean (CSB) and soya bean oil cake (SBC) were fed on equi-protein basis. The results showed that: 1. Red blood cell (RBC) count and haemoglobin content of blood significantly (P less than 0.05) increased in chicks fed RSB relative to the other soya bean diets. Feeding differently processed soya bean significantly (P less than 0.05) influenced mean cell haemoglobin (MCH) and mean corpuscular volume (MCV) while the mean corpuscular haemoglobin concentration (MCHC) was not significantly influenced. 2. Both the total white blood cell (WBC) count and the monocytes were significantly (P less than 0.05) influenced by the dietary treatments. Chicks fed processed soya bean generally had higher number of monocytes. 3. Physical properties determined were specific gravity and erythrocyte sedimentation rate. The latter was significantly (P less than 0.05) lower in all the processed soya bean-fed chicks. 4. Minerals determined in blood were Na, K, Ca, Mg, Fe, Cu and P. Of all these, chicks fed RSB had significantly (P less than 0.01) lower levels of blood Mg and marked decrease in Ca.

Repair of microvilli in the rat small intestine after damage with lectins contained in the red kidney bean

That microvilli of intestinal absorptive cells in the duodenum and jejunum are disrupted by acute challenge with lectins contained in raw kidney beans (RKB) was shown nearly 10 yr ago by light microscopy. However, the precise morphologic damage produced by RKB has not been characterized, and it is not known whether microvilli, once damaged, undergo repair. We have examined these issues by challenging rats with suspensions of 300 mg of RKB, boiled beans, or standard laboratory chow by orogastric lavage. Microvillus length was measured in electron micrographs from 6 to 20 h after challenge. Epithelial cell migration was determined by autoradiography after injection of [3H]thymidine. After challenge with RKB, microvilli (a) showed extensive vesiculation along the length of villi 2-4 h after challenge; (b) were reduced significantly in length along the entire villus 6 h after challenge; and (c) were near normal in length by 20 h after challenge. Microvillus length was also reduced significantly 6 h after challenge with boiled beans. The rate of cell migration was not accelerated by treatment with RKB. These data suggest that damage to microvilli caused by 300 mg of RKB is self-limited and reversible; microvilli once damaged by RKB are repaired. Repair of microvilli is due to intrinsic reparative processes rather than accelerated replacement of damaged cells. We speculate that microvilli may be repeatedly damaged and repaired after ingestion of dietary lectins.