I. Pallarés

Effect of iron deficiency on the digestive utilization of iron, phosphorus, calcium and magnesium in rats

The influence of the source of dietary Fe (ferric citrate alone or mixed with bovine blood at a proportion of 1:1 (v/v)) on the digestive utilization of Fe, P, Ca and Mg, and on haemoglobin regeneration efficiency (HRE) was investigated in control and Fe-deficient rats. Diet A contained (by analysis) 43.5 mg Fe/kg diet (as ferric citrate), and diet B contained 44.3 mg Fe/kg diet (ferric citrate-bovine blood). In Fe-deficient rats fed on diet A or B the apparent digestibility coefficient (ADC) of Fe increased by 42.3 and 45.7% respectively. The ADC of Ca and Mg decreased significantly in Fe-deficient rats regardless of the source of dietary Fe. The HRE increased by 72.9% in Fe-deficient rats fed on diet A, and by 91.1% in Fe-deficient animals fed on diet B. In Fe-deficient rats fed on Fe for 10 d the values of haematological variables approached normality. However, serum Fe remained low, indicating that Fe reserves were still depleted. A deficient dietary supply of Fe for 30 d did not significantly modify the numbers of circulating leucocytes.

The absorption of iron, calcium, phosphorus, magnesium, copper and zinc in the jejunum–ileum of control and iron-deficient rats

The effects of iron deficiency on the absorption of different dietary sources of iron were studied, together with the interactions between iron, calcium, phosphorus, magnesium, copper and zinc in the jejenum–ileum of control and iron-deficient rats. In this study, three perfusion solutions containing different iron sources: ferric citrate, haemoglobin, and equal parts of ferric citrate and haemoglobin were used. In addition, the same perfusion solutions were used with and without 2,4-dinitrophenol, an inhibitor of oxidative phosphorylation. Iron absorption in anaemic rats was greater than in the controls, except after perfusion with solutions containing haemoglobin. The absorption of calcium, copper and zinc in iron-deficient animals was not significantly affected, while the absorption of phosphorus and magnesium increased, with respect to animals in the control group. After perfusion with solutions containing haemoglobin, the absorption values of calcium, copper and zinc were lower than after ferric citrate in both groups (control and iron-deficient rats).

Bioavaliability of Fe, Ca, P and Mg in Fe-deficient rats treated with different sources of dietary iron

Abstract Iron deficiency (D0) markedly decreases the concentration of iron and calcium in the liver, femur and sternum. We investigated the effect of the source of dietary iron [ferric citrate alone (citrate diet), or combined with bovine blood at a proportion of 1:1 (citrate + heme diet), and ferric protein (protein-Fe diet)] on the nutritive utilization of Fe, Ca, P and Mg in anemic and healthy rats. All diets contained the same amount of Fe (40 mg/kg diet). In Fe-deficient rats (DT) fed citrate, citrate + heme or protein-Fe diet the apparent digestibility coefficient (ADC) of Fe were 39%, 37% and 94% greater than in the respective control groups (C); hemoglobin regeneration efficiencies (HRE) were respectively 47%, 51%, and 172% greater than in the control groups. The ADC of Ca was not affected by Fe deficiency, whereas the ADC of Mg decreased significantly, and that of P increased under our experimental conditions. In Fe-deficient rats fed Fe for 10 days (DT), the concentrations of hemoglobin approached normal values. However, serum Fe remained low, indicating that Fe reserves were still depleted. Hepatic and femoral Fe concentrations were also lower in all DT groups, whereas Fe concentrations in the sternum increased significantly, suggesting an increase in erythropoiesis. After supply of dietary Fe for 10 days in iron-deficient groups (DT), Ca and P concentrations increased in sternum, a site assumed to have higher requirements for these minerals. In the liver these values tended to normalize, whereas in the femur Ca and P stores remained depleted. Mg concentrations after the replenishment period generally approached normality in all three organs.

Role of the proximal colon in mineral absorption in rats with and without ferropenic anemia

Abstract We studied the effects of iron deficiency on the absorption of different dietary sources of iron in vivo (non-heme, heme, and equal parts of both forms), and investigated the interactions between iron and calcium, phosphorus, magnesium, copper and zinc in the proximal colon of control and iron-deficient rats. Three perfusion solutions containing a different source of iron were used: solution 1, ferric citrate; solution 2, hemoglobin; solution 3, equal parts of ferric citrate and hemoglobin. We also tested the same perfusion solutions with 2,4-dinitrophenol (2,4-DNP), an inhibitor of oxidative phosphorylation (solutions 1-I, 2-I and 3-I). In control rats we observed three mechanisms of iron absorption: passive for soluble iron salts, active receptor-mediated for inorganic Fe complexes, and active receptor-mediates for heme iron. In anemic rats iron absorption was greater than in controls, except after perfusion with solution 2 (containing hemoglobin). Absorption increased as a result of the passive mechanism. The active component was influenced by the depletion of heme receptors under severe iron deficiency. The absorption of calcium, phosphorus, magnesium, copper and zinc was greater in iron-deficient animals than in the control group. After perfusion with solution 2 or 3, calcium, copper and zinc absorption were lower than after solution 1. We conclude that ferropenic anemia leads to increased absorption by the proximal colon of all minerals studied. This increase is due mainly to the passive route of absorption.

Supplementation of a Cereal-Milk Formula with Haem Iron Palliates the Adverse Effects of Iron Deficiency on Calcium and Magnesium Metabolism in Rats

Aside from the well known alteration of Fe status in Fe deficiency, this condition has also a negative effect on the bioavailability of Ca and Mg. We studied the influence of the supplementation of a commercial cereal-milk formula with bovine blood on Fe, Ca, P, and Mg metabolism in control and Fe-deficient rats to investigate whether high Fe levels in diet produce some interactions and the possibility of decreasing these latter by a haem-Fe supplementation. The bioavailability in control and Fe-deficient animals was determined as the apparent digestibility coefficient and hemoglobin regeneration efficiency, both of which are accurate estimations of total Fe utilization. Non-fortified cereal-milk formula decreased the apparent digestibility coefficient of Ca and Mg in Fe-deficient rats; the concentrations of these minerals in liver, femur, and sternum were lower than in control animals. However, when the Fe content of the cereal-milk formula was doubled by supplementation with bovine blood, the adverse effects on the digestive utilization of Ca, and especially of Mg, were palliated, the concentration of these two minerals in the organs investigated increased, and the overall Fe status improved in Fe-deficient rats.

Zinc metabolism in rats: Effects of intestinal resection, cholecalciferol and ascorbic acid

Abstract The metabolic balance technique was used to study the effect of dietary composition on zinc nutritive utilization in rats in which 50% of the distal small intestine (DSI) was removed, and in transected rats (controls). Six experiments with three different diets were done: the basal diet contained 12% protein (casein+5% D,L-methionine) and 4% lipid (medium chain triglycerides (MCT), olive oil and sunflower oil in equal parts); the other two diets were obtained by supplementing the basal diet with cholecalciferol (0.4 mg/kg diet) or adding ascorbic acid (150 mg/kg diet). Resection of 50% of the DSI markedly affected the digestive and metabolic utilization of zinc [apparent digestibility coefficient (ADC), and zinc balance] in rats fed on the basal diet alone or additioned with vitamin C. However, these parameters were not so markedly affected by the surgery in rats whose diet was supplemented with cholecalciferol. To investigate postresection zinc homeostasis we also measured the concentrations of this metal in blood, plasma and several organs (liver, femur, sternum, longissimus dorsi (LD) muscle and testes) one month after surgery. We found no alterations in the distribution of zinc in the organism under any of the experimental conditions. We conclude that the adaptive mechanisms that maintaining trace metal homeostasis are operative one month after intestinal resection.

Effects of intestinal resection, cholecalciferol and ascorbic acid on iron metabolism in rats

The effect of dietary supplementation with ascorbic acid or cholecalciferol on Fe utilization was studied using the metabolic balance technique, in rats in which 50% of the distal small intestine was removed, or in which the mid small intestine was transected and reanastomosed (controls). Three different diets were used. The first (basal diet) contained (g/kg dry wt): protein (casein + 50 mg D,L-methionine/g) 120 and fat (medium-chain triacylglycerols, olive oil and sunflower oil, in equal parts) 40. The other diets were obtained by adding ascorbic acid (150 mg/kg diet) or cholecalciferol (0.4 mg/kg diet) to the basal diet. Apparent digestibility coefficient (ADC) and Fe retention were significantly lower in resected animals than in their respective control groups (transected rats). However, the addition of ascorbic acid or cholecalciferol to the basal diet increased the ADC and Fe retention in both transected and resected rats. Five weeks after surgery, resection also resulted in a reduced concentration of Fe in the sternum, but did not reduce the concentration of haemoglobin or serum Fe total Fe-binding capacity or the concentration of Fe in liver, testes, femur or muscle (longissimus dorsi). Supplementation with ascorbic acid increased serum Fe concentration, while the concentration of Fe in muscle was reduced by supplementation with both ascorbic acid and cholecalciferol. Neither supplementation had any effect on the Fe concentration in other tissues, on haemoglobin concentration or plasma total Fe-binding capacity. Thus, supplementation with ascorbic acid or with cholecalciferol increased Fe absorption and reduced the concentration of Fe in muscle.

Copper malabsorption after intestinal resection in rats. Effects of cholecalciferol and ascorbic acid.

Dietary modifications can partly compensate for the alterations in copper homeostasis caused by distal intestinal resection, by improving biliary function. We studied the effects of resecting 50% of the distal small intestine (DSI) on copper status in rats fed three semisynthetic diets (basal diet, and basal diet with cholecalciferol or ascorbic acid). Intestinal resection significantly decreased the digestive (apparent digestibility coefficient; ADC) and metabolic utilization (balance) of copper 1 month after surgery. However, the supplementation of the basal diet with cholecalciferol attenuated the negative impact of surgery, leading to small differences in Cu ADC and Cu balance between transected and resected rats. Ascorbic acid also enhanced copper retention. Copper status was not as markedly affected by intestinal resection as digestive utilization 1 month after the operation. The beneficial effects of cholecalciferol and ascorbic acid at the digestive and metabolic levels suggest ways to lessen the impact of intestinal resection, and to avoid possible long-term postabsorptive alterations in copper distribution.

Effect of intestinal resection, type of dietary fat and time on biliary lipid secretion in rats.

The effects of time and the type of dietary fat on biliary physiology in rats with 50% resection of the distal small intestine were investigated. The effects of ursodeoxycholic acid as an exogenous source of bile acid added to the diet were also studied. The fat composition of all diets was the same in quantitative terms (4%), and differed only in the type of lipid supplied: olive oil (diet A) or one‐third medium chain triglycerides, one‐third sunflower seed oil and one‐third olive oil (diet B). In resected rats given diet A for 1 or 3 months, there was a decrease in biliary secretion of cholesterol and phospholipids, and in the lithogenic index, with respect to the control group. Resected rats fed diet B for 1 or 3 months showed increases in biliary secretion of cholesterol and phospholipids, and in the lithogenic index, in comparison with resected rats fed diet A. The addition of ursodeoxycholic acid to diet B led to the decoupling of bile acid and bile lipid secretion.