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PubMed2001

Magnesium absorption using stable isotope tracers in healthy children and children treated for leukemia.

Intestinal magnesium (Mg) absorption was measured in six healthy children (control) and in four children treated for acute lymphoblastic leukemia with the single-isotope fecal recovery technique (SIFRT). The objective of this study was to determine Mg absorption in young children with acute lymphoblastic leukemia using stable isotope tracers. Fractional and absolute absorption levels determined by SIFRT were not significantly different between children with acute lymphoblastic leukemia (fractional absorption: 58.3 +/- 10.6% [mean +/- SEM], absolute absorption: 3.66 +/- 0.71 mg x kg(-1) x d(-1), [0.15 +/- 0.03 mmol x kg(-1) x d(-1)]) and control children (fractional absorption: 61.4 +/- 7.5%, absolute absorption: 5.69 +/- 0.85 mg x kg(-1) x d(-1), [0.23 +/- 0.03 mmol x kg(-1) x d(-1)]). Average Mg absorption in young children (aged 3--8 y) was 60.2 +/- 5.8%. This study describes the first application of the SIFRT to assess Mg absorption in young children and illustrates the feasibility of the SIFRT in this age group to obtain more accurate information on Mg absorption.

Case-Control Studies↗
PubMed1980

Total intestinal absorption of glucose and L-methionine in broilers infected with Eimeria acervulina, E. mivati, E. maxima or E. brunetti.

The in vitro absorption of glucose and L-methionine in the intestine of broiler chickens was measured 7, 14 and 21 days post-inoculation (p.i.) with sporulated oocysts of Eimeria acervulina, E. mivati, E. maxima or E. brunetti. The small intestine of each bird was divided into 8 regions of equal length and absorption was measured on 3 tissue disks of equal size from each region. The absorption rate of each substrate with each coccidial species was measured based on (1) an equal area from each region, (2) an equal weight from each region, (3) the total absorption in each region, and (4) the total potential absorption in the intestine. Comparisons of absorption rate of equal areas in each intestinal region demonstrated that infected birds at 7 days p.i. absorbed significantly less substrate per unit area in the regions of maximum infection than uninfected controls. Malabsorption was less apparent when the weight of the region was used as the unit of measurement. Compensatory absorption was seen in some uninfected regions with E. acervulina. The total potential intestinal absorption at 7 days p.i. was reduced with E. mivati, E. maxima and E. brunetti but not with E. acervulina. At 14 days p.i., total L-methionine and glucose absorption in some regions of the intestine was significantly increased with E. acervulina but not with E. mivati, E. maxima or E. brunetti. No absorption differences were seen at 21 days p.i. with any species.

Animals↗
PubMed2001

Time-dependent oral absorption models.

The plasma concentration-time profiles following oral administration of drugs are often irregular and cannot be interpreted easily with conventional models based on first- or zero-order absorption kinetics and lag time. Six new models were developed using a time-dependent absorption rate coefficient, ka(t), wherein the time dependency was varied to account for the dynamic processes such as changes in fluid absorption or secretion, in absorption surface area, and in motility with time, in the gastrointestinal tract. In the present study, the plasma concentration profiles of propranolol obtained in human subjects following oral dosing were analyzed using the newly derived models based on mass balance and compared with the conventional models. Nonlinear regression analysis indicated that the conventional compartment model including lag time (CLAG model) could not predict the rapid initial increase in plasma concentration after dosing and the predicted Cmax values were much lower than that observed. On the other hand, all models with the time-dependent absorption rate coefficient, ka(t), were superior to the CLAG model in predicting plasma concentration profiles. Based on Akaike's Information Criterion (AIC), the fluid absorption model without lag time (FA model) exhibited the best overall fit to the data. The two-phase model including lag time, TPLAG model was also found to be a good model judging from the values of sum of squares. This model also described the irregular profiles of plasma concentration with time and frequently predicted Cmax values satisfactorily. A comparison of the absorption rate profiles also suggested that the TPLAG model is better at prediction of irregular absorption kinetics than the FA model. In conclusion, the incorporation of a time-dependent absorption rate coefficient ka(t) allows the prediction of nonlinear absorption characteristics in a more reliable manner.

Administration, Oral↗
PubMed1995

Different effects of absorption promoters on corneal and conjunctival penetration of ophthalmic beta-blockers.

PURPOSE: The purpose of this study was to investigate the improvement in corneal penetration of ophthalmic beta-blockers of various lipophilicities afforded by absorption promoters and to compare the corneal against conjunctival penetration in response to absorption promoters. METHODS: The penetration of the beta-blockers, atenolol, carteolol, tilisolol, timolol, and befunolol, in the presence of absorption promoters, across the isolated corneal and conjunctival membranes of albino rabbits was measured using a two-chamber glass diffusion cell. EDTA, taurocholic acid, capric acid, and saponin were used as the absorption promoters. RESULTS: The absorption promoters significantly increased the corneal permeability of most beta-blockers, especially the hydrophilic agents. The absorption promoters also enhanced the conjunctival permeability of beta-blockers, although their effect in promoting conjunctival penetration was less than that on corneal penetration. There was a differing penetration of instilled beta-blockers in the cornea and conjunctiva in response to absorption promoters. Capric acid and saponin showed significant promoting action on corneal penetration, but not on conjunctival penetration. Taurocholic acid had a significant effect on conjunctival penetration but not on corneal penetration. Saponin caused slight irritation. CONCLUSIONS: Absorption promoters can improve the ocular delivery of beta-blockers and a selective use of absorption promoter can improve the extent and pathway of drug ocular absorption.

Absorption↗
PubMed1997

Modeling of subcutaneous absorption kinetics of infusion solutions in the elderly using technetium.

Absorption kinetics of solutes given with the subcutaneous administration of fluids is ill-defined. The gamma emitter, technitium pertechnetate, enabled estimates of absorption rate to be estimated independently using two approaches. In the first approach, the counts remaining at the site were estimated by imaging above the subcutaneous administration site, whereas in the second approach, the plasma technetium concentration-time profiles were monitored up to 8 hr after technetium administration. Boluses of technetium pertechnetate were given both intravenously and subcutaneously on separate occasions with a multiple dosing regimen using three doses on each occasion. The disposition of technetium after i.v. administration was best described by biexponential kinetics with a Vss of 0.30 +/- 0.11 L/kg and a clearance of 30.0 +/- 13.1 ml/min. The subcutaneous absorption kinetics was best described as a single exponential process with a half-life of 18.16 +/- 3.97 min by image analysis and a half-life of 11.58 +/- 2.48 min using plasma technetium time data. The bioavailability of technetium by the subcutaneous route was estimated to be 0.96 +/- 0.12. The absorption half-life showed no consistent change with the duration of the subcutaneous infusion. The amount remaining at the absorption site with time was similar when analyzed using image analysis, and plasma concentrations assuming multiexponential disposition kinetics and a first-order absorption process. Profiles of fraction remaining at the absorption site generated by deconvolution analysis, image analysis, and assumption of a constant first-order absorption process were similar. Slowing of absorption from the subcutaneous administration site is apparent after the last bolus dose in three of the subjects and can be associated with the stopping of the infusion. In a fourth subject, the retention of technetium at the subcutaneous site is more consistent with accumulation of technetium near the absorption site as a result of systemic recirculation.

Absorption↗
PubMed1985

Effects of acute and chronic treatment with glucocorticoids on the intestinal absorption of calcium and phosphate and on plasma 1,25-dihydroxyvitamin D levels in pigs.

We have used young pigs, each prepared surgically with a Thiry-Vella loop of proximal small intestine, to study the time course of changes in the intestinal absorption of calcium, phosphate, sodium, glucose and water and on the plasma levels of 1,25-dihydroxyvitamin D after treatment of the animals with glucocorticoids. Perfusion of the intestinal loop for 6 h with a solution containing hydrocortisone or beta-methasone was without effect on the absorption of calcium or phosphate. The oral administration of betamethasone stimulated the absorption of calcium and phosphate by 15-20% for 2-3 days before the trend was reversed and absorption was progressively reduced. Chronic treatment with betamethasone inhibited only the active component of calcium and phosphate absorption. Treatment with betamethasone was associated with a sustained 25-50% increase, to a maximum by 2 days, in the absorption of sodium, glucose and water. Plasma levels of 1,25-dihydroxyvitamin D were reduced within 2 days of the start of treatment and reached a minimum (40-50% decrease) in 4-6 days. We conclude that the initial stimulation of calcium and phosphate absorption is caused by the increased absorption of water. The long-term decrease in absorption may not be caused solely by the decreased circulating levels of 1,25-dihydroxyvitamin D since absorption continued to fall for several weeks after 1,25-dihydroxyvitamin D levels had reached a minimum.

Animals↗
PubMed1999

In vitro absorption studies with carvedilol using a new model with porcine intestine called BM-RIMO (Boehringer-Mannheim ring model).

Carvedilol (CAS 72956-09-3, Dilatrend) is a beta-blocker with additional vasodilating, antiproliferative and antioxidative properties. It is indicated for the treatment of high tension (HT), coronary artery disease (CAD) and congestive heart failure (CHF). Carvedilol has been investigated in numerous in vivo studies and thus comparisons of in vitro results to in vivo observations are possible. In this publication the results of studies on the in vitro absorption of carvedilol in a new model called BM-RIMO (Boehringer-Mannheim ring model) using porcine intestine are reported. In particular the influence of absorption enhancers and of pH and the existence of absorption windows were examined and the relevance of the obtained data for in vivo conditions was estimated. The main route of carvedilol absorption seemed to be transcellular. In vitro as well as in vivo absorption decreased within the intestine in the following order: jejunum > ileum > colon. The highest amount of in vitro absorption of carvedilol was achieved in the jejunum at a neutral pH. Enhancers such as bile and the mucoadhesive agent chitosan had opposite effects on the absorption of the compound. The results indicate that BM-RIMO is a simple, cheap and fast tool for the investigation of the influence of absorption enhancers, pH and different parts of intestine on absorption. For carvedilol the in vitro model tends to overestimate absorption in the colon, possibly because of the lack of faeces.

Adolescent↗
PubMed1980

Studies on the absorption of zinc by rat intestine.

1. A technique is described for the measurement of the extent of 65Zn absorption by different regions of the intestine in the intact rat. Using this technique it was shown that the duodenum contributed 60%, the ileum 30% and the jejunum 10% to the over-all absorption of 65Zn. Negligible absorption of 65Zn occurred from the caecum and colon. 2. Using ligated loops of rat duodenum in situ, 65Zn absorption was shown to be rapid, with 1% of a 5 microgram dose being transferred to the carcase within 1 min of intraluminal dosing. 3. When 65Zn was injected into ligated loops in a dose range of 1--200 microgram Zn/ml the rate of absorption was linear with respect to time over the first 15 min. The rates of 65Zn absorption v. dose of 65Zn exhibited saturation kinetics indicating absorption by a 'carrier' or enzyme-mediated process. 4. The binding of 65Zn to loop tissue showed biphasic kinetics which suggested that at low intraluminal concentrations of Zn (1--50 microgram Zn/ml) binding was to specific sites whereas, at higher concentrations (50--200 microgram Zn/ml), non-specific binding occurred. 5. A study of the fate of mucosally bound 65Zn showed that over the first 30 min a proportion of the 65Zn was rapidly transferred to the carcase and this was probably associated with the rapid phase of 65Zn absorption described previously. From 30 min up to 6 h after the initial binding, 65Zn was also transferred to the carcase albeit at a much slower rate indicating a slow phase of Zn absorption. A study of the kinetics of this slow phase indicated that the loss of bound 65Zn to the body was a saturable process indicating an enzyme- or 'carrier'-mediated process. A comparison of the kinetics of the slow and rapid phases of 65Zn absorption suggests that these processes are distinct. 6. Histological examination of mucosal tissue of loops exposed to 200 microgram Zn/ml revealed to discernable diamage. Similarly, no effect was observed on either arginine or glucose uptake by isolated duodenal loops in situ, although this concentration of Zn completely abolished fluid uptake. A study of the effect of different doses of Zn showed that 50 microgram Zn/ml inhibited mucosal fluid uptake by more than 50% and 100 microgram Zn/ml by more than 90%. It was concluded that these effects were due to a specific action on the fluid-transfer process and not due to a general poisoning of the mucosa.

Animals↗
PubMed1996

Increases in calcium absorption with ingestion of soluble dietary fibre, guar-gum hydrolysate, depend on the caecum in partially nephrectomized and normal rats.

Effects of feeding soluble dietary fibre on apparent Ca absorption and the contribution of the caecum to Ca absorption were examined in five-sixths nephrectomized (NPX) and normal rats with or without caecectomy in four experiments. It is known that Ca absorption is lowered by renal failure. In the first experiment the amounts of femur Ca increased linearly with increasing dietary Ca up to 3.0 g Ca/kg diet in intact rats. Partial nephrectomy decreased apparent Ca absorption in rats fed on diets containing 3-0 and 4.5 g Ca/kg diet. In the NPX groups, Ca absorption in rats fed on the diet containing guar-gum hydrolysate (GGH; 50 g/kg diet; 3.0 g Ca/kg diet) was significantly higher than that in rats fed on a fibre-free diet, and the increase in Ca absorption with GGH feeding was completely abolished by caecectomy. Also, ingestion of GGH increased Ca absorption in normal rats, but not in normal, caecectomized rats. Mg absorption was also increased with GGH feeding and was decreased with caecectomy in NPX and normal rats. In experiments which used caecectomized rats, coprophagy was prevented with an anal cup to avoid re-ingestion of faecal Ca. We conclude that ingestion of the soluble dietary fibre, GGH, increased apparent Ca absorption in NPX and non-NPX rats, and the caecum was responsible for these increases in Ca absorption.

Animals↗
PubMed2002

Phytate degradation determines the effect of industrial processing and home cooking on iron absorption from cereal-based foods.

The aim of the present study was to compare Fe absorption from industrially-manufactured and home-cooked cereal foods. Fe absorption was measured using the radiolabelled Fe extrinsic tag technique in thirty-nine adult human subjects from cereal porridges manufactured by extrusion cooking or roller-drying, and from the same cereal flours after home cooking to produce pancakes, chappattis or bread. One series of cereal porridges was amylase-treated in addition before roller-drying. Fe absorption was relatively low from all products, ranging from 1.8-5.5 % for rice, 2.5-3.5 % for maize, 4.9-13.6 % for low-extraction wheat, and <1 % for high-extraction wheat foods. The phytic acid content remained high after drying of the cereal porridges being about 1.20, 1.70, 3.20, 3.30 mg/g in low-extraction wheat, rice, high-extraction wheat and maize products respectively, and could explain the low Fe absorption. There were little or no differences in Fe absorption between the extruded and roller-dried cereals, although amylase pre-treatment increased Fe absorption from the roller-dried rice cereal 3-fold. This was not due to phytate degradation but possibly because of the more liquid nature of the cereal meal as fed. There were similarly few or no differences in Fe absorption between the industrially-processed cereals and home-cooked cereals made into pancakes or chappattis. Bread-making, however, degraded phytic acid to zero in the low-extraction wheat flour and Fe absorption increased to 13.6 %, the greatest from all cereal foods tested. It is concluded that Fe absorption from extruded, roller-dried or home-cooked cereal foods is similarly low and that only those cooking procedures such as bread-making, which extensively degrades phytic acid, or amylase pre-treatment, which substantially liquifies cereal porridges, improve Fe absorption.

Adult↗
PubMed2006

Effect of beef and soy proteins on the absorption of non-heme iron and inorganic zinc in children.

BACKGROUND: Iron and zinc deficiency remain substantial problems in small children in both developed and developing nations. Optimizing mineral absorption is an important strategy in minimizing this problem. OBJECTIVES: To assess the effects of beef and soy proteins on the bioavailability of non-heme iron and zinc in children. METHODS: We measured iron (n = 26) and zinc (n = 36) absorption in 4-8 y old children from meals differing only in protein source (beef or a low-phytate soy protein concentrate). Iron and zinc absorption were measured using multi-tracer stable isotope techniques. Iron absorption was calculated from the red blood cell iron incorporation measured after 14 days and zinc absorption from the ratio of the oral and intravenous excretion of the zinc tracers 48 hours after dosing. RESULTS: Iron absorption from the beef meal was significantly greater (geometric mean, 7.6%) than from the soy meal (3.5%, p = 0.0015). Zinc absorption from the beef meal was greater (mean +/- SD, 13.7 +/- 6.0%) than from the soy meal (10.1 +/- 4.1%, p = 0.047). CONCLUSION: These findings indicate that beef protein increases both non-heme iron and zinc absorption compared to soy protein. The effect of protein source on non-heme iron and inorganic zinc absorption should be one of the factors taken into account when designing diets for children. The inhibitory effect of the soy based meal on iron and zinc absorption could be overcome by fortifying the soy protein with these minerals during the production process.

Biological Availability↗
PubMed1984

Effects of iron, tin, and copper on zinc absorption in humans.

Zinc absorption as measured by body retention of [65Zn]zinc chloride or a turkey test meal extrinsically labeled with 65Zn was determined in human subjects by whole body counting after 7 days. Average 65Zn absorption from zinc chloride in persons with a high iron-absorbing capacity was similar to persons with a low capacity to absorb iron. Inorganic iron, 920 mumol (51 mg), or HB iron, 480 mumol (26 mg), inhibited 65Zn absorption from 92 mumol (6 mg) of zinc chloride. When 610 mumol of iron (34 mg) was added to a turkey test meal containing 61 mumol of zinc (4 mg), 65Zn absorption was not inhibited. Tin, 306 mumol (36 mg), given with zinc chloride or turkey test meals (61 mumol, 4 mg, of Zn) significantly reduced 65Zn absorption. Copper, 79 mumol (5 mg), had no significant effect on the 65Zn absorption from 7.9 mumol (0.5 mg) of zinc chloride. In summary, the capacity to absorb iron did not influence 65Zn absorption, but both inorganic iron and heme-iron inhibited 65Zn absorption from zinc chloride. Inorganic iron had no effect, however, on 65Zn absorption from the turkey test meal. Tin in a large dose also inhibited 65Zn absorption from both zinc chloride and the turkey test meal.

Adolescent↗
PubMed1985

Enhancement of calcium absorption in rats by coadministration of glucose polymer.

Glucose polymer derived from corn starch is widely used in infant formula and nutritional supplements as a readily digestible, low osmolarity source of calories. We have previously observed that glucose polymer causes a marked increase in intestinal calcium absorption in patients with intestinal malabsorption and in normal subjects. The present study investigates the effect of concurrently administered glucose polymer on intestinal 45calcium absorption in rats. The effect of glucose polymer on calcium absorption was compared to that of equivalent doses of dextrose or lactose. Femur radioactivity was determined as an index of calcium absorption. Carbohydrates were prepared at doses of 0.5, 2.0 and 4.0 mg/g body weight and administered with 45Ca by stomach gavage. Control rats received 45Ca in water alone. Coadministration of glucose polymer resulted in a dose-dependent increase in calcium absorption. At the highest dose of polymer studied calcium absorption was 75% greater than in control animals. Administration of lactose and dextrose also resulted in a dose-dependent increase in calcium absorption. Calcium absorption was 122 and 67% greater than controls when 4 mg/g BW lactose and dextrose were given with the 45Ca. We conclude that glucose polymer stimulates calcium absorption in rats similar to lactose and glucose. These results suggest that glucose polymer may be a useful therapeutic adjunct in patient groups in which there is a desire to increase intestinal calcium absorption.

Animals↗
PubMed1988

Variability of calcium absorption.

Variability in calcium absorption was estimated in three groups of normal subjects in whom Ca absorption was measured by standard isotopic-tracer methods at interstudy intervals ranging from 1 to 4 mo. Fifty absorption tests were performed in 22 subjects. Each was done in the morning after an overnight fast with an identical standard breakfast containing a Ca load of approximately 250 mg. Individual fractional absorption values were normalized to permit pooling of the data. The coefficient of variation (CVs) for absorption for the three groups ranged from 10.57 to 12.79% with the size of the CV increasing with interstudy duration. One other published study presenting replicate absorption values was analyzed in a similar fashion and was found to have a CV of absorption of 9.78%. From these data we estimate that when the standard double-isotope method is used to measure Ca absorption there is approximately 10% variability around any given absorption value within an individual human subject and that roughly two-thirds of this represents real biological variability in absorption.

Absorption↗
PubMed2003

High-, but not low-bioavailability diets enable substantial control of women's iron absorption in relation to body iron stores, with minimal adaptation within several weeks.

BACKGROUND: Adaptation of iron absorption in response to dietary iron bioavailability is less likely in premenopausal women, who generally have lower iron stores, than in men. OBJECTIVE: The objective of the study was to ascertain whether iron absorption in women adapts to dietary iron bioavailability and whether adaptation reflects altered absorptive efficiency or adjustment to specific inhibitors or enhancers of absorption. DESIGN: Heme- and nonheme-iron absorption from either high- or low-bioavailability diets was measured at 0 and 10 wk in premenopausal women as they consumed one of the diets for 12 wk (randomized 2 x 2 factorial design). The high- and low-bioavailability diets contained similar amounts of total iron, as 13.1 and 14.8 mg/d nonheme and 2.0 and 0.3 mg/d heme iron, respectively, and they differed in contents of meat, ascorbate, whole grains, legumes, and tea. RESULTS: In premenopausal women, the efficiency of nonheme-iron absorption (P = 0.06, two-tailed test), but not of heme-iron absorption, tended to adapt in response to a 12-wk difference in dietary iron bioavailability, whether absorption was tested with high- or low-bioavailability menus. Bioavailability, but not adaptation, substantially influenced total iron absorption (approximately 6-fold). In contrast with iron absorption from the low-bioavailability diet, that from the high-bioavailability diet consistently was inversely associated with serum ferritin. CONCLUSION: Only the high-bioavailability diet enabled women to absorb more iron in relation to their low iron stores. Women consuming the high-bioavailability diet absorbed up to 4.5 mg (30-35%) dietary iron with minimal influence of the diet consumed during the previous 10 wk.

Adaptation, Physiological↗
PubMed2004

Effect of a micronutrient fortificant mixture and 2 amounts of calcium on iron and zinc absorption from a processed food supplement.

BACKGROUND: Iron, zinc, and calcium can interact with each other in a way that inhibits their respective absorption. On the other hand, mineral fortification has been used to improve simultaneous iron and zinc absorption from food supplements. OBJECTIVE: We evaluated the effect of a novel fortificant mixture consisting of NaFeEDTA, zinc methionine, ascorbic acid, and citric acid on iron and zinc absorption from a dry food supplement designed for preschool children. DESIGN: The standard food supplement contained cereal and legume flour, dried milk, and a mixture of micronutrients including ferrous sulfate and zinc sulfate as sources of supplemental iron and zinc, respectively. Standard and novel food products were prepared as porridge with or without the addition of 200 mg Ca as calcium phosphate. Iron absorption and zinc absorption from the food products were evaluated simultaneously in 13 nonpregnant, adult women by extrinsically labeling the products with radioisotopes of iron and zinc and carrying out whole-body counting 7 d after the food products were consumed in random order. RESULTS: The absorption of iron from the NaFeEDTA-containing (novel) food product was 1.7 times that from the ferrous sulfate-containing (standard) product (P = 0.015). There was no significant effect of dietary calcium on iron absorption. Zinc absorption was not associated with the form of zinc consumed, but higher dietary calcium was marginally associated with lower zinc absorption (P = 0.071). CONCLUSIONS: A mixture of fortificants containing NaFeEDTA, zinc sulfate or zinc methionine, ascorbic acid, and citric acid, but without calcium, can improve iron and zinc absorption from food products. A cost-benefit analysis of the novel fortificant mixture needs to be performed.

Adult↗
PubMed1984

Effect of phosphate on the intestinal absorption of lead (203Pb) in chicks.

The effect of phosphate on the intestinal absorption of lead (203Pb2+) was examined in chicks. Absorption was determined by the in situ ligated duodenal loop technique. In one approach, diets differing in phosphate content were fed to 2-week-old chicks for a period of 7 days. With respect to the control group (1.06% P), a severe phosphate deficiency (0.16% P) decreased growth, CaBP synthesis and 203Pb absorption; a moderate phosphate deficiency (0.33% P) resulted in an increase in CaBP production and 203Pb absorption; and the high phosphate diet (2.12%) gave mean values for CaBP synthesis and 203Pb absorption intermediate between those from the chicks fed the 0.33 and 1.06% diets. 203Pb absorption was highly correlated with CaBP concentrations. In another approach, phosphate in varying concentrations was added directly to the dosing solution. In one study, phosphate addition (0.1 mM) depressed 203Pb absorption in rachitic and cholecalciferol-treated chicks. When the data were expressed in terms of absorption of the soluble 203Pb present in the intestinal lumen at the end of the absorption period, an effect of phosphate in addition to the precipitation of the insoluble lead salt was uncovered. In an experiment with normal chicks, it was observed that phosphate in the dosing solution at concentrations of 1 and 2 mM partially and significantly reversed the inhibitory effect of lower concentrations of phosphate (0.01 mM and 0.1 mM). These data demonstrate the complexity of the phosphate-lead interaction, in addition to directly showing an effect of dietary phosphate on intestinal lead absorption.

Animals↗
PubMed1986

Comparative studies of selenium-75 (selenite and selenomethionine) absorption from various milk diets in suckling rats.

Selenium (Se) absorption was studied in human milk, bovine milk and infant formula (Similac) using suckling rats as a model. The effect of age on Se absorption from the three milk diets extrinsically labeled with 75Se, either as selenite or selenomethionine, was also investigated. Milk diets were fed by gastric intubation and the radioactivity in the carcass, gastrointestinal tract and the liver were measured 3 h after feeding. There was no difference in [75Se]selenite absorption from the three milk diets between 8-20 d of age. However, significantly higher quantity of 75Se was absorbed from all three milk diets by 20-d-old rats than by the younger rats (46 vs. 32%). This increase in [75Se]selenite absorption with advancing age is opposite to what has been found for most other trace elements. When rats were fed milk diets labeled with [75Se]selenomethionine, the absorption of 75Se was approximately twofold higher in all age groups compared with 75Se absorption from selenite. No difference in [75Se]selenomethionine absorption existed among the three milk diets in 8- or 10-d-old suckling rats. However, at 15 d of age [75Se]selenomethionine absorption from human milk was higher (82%) than from either bovine milk (72%) or infant formula (72%). Between 8 and 20 d of age, absorption of [75Se]selenomethionine from the three milk diets decreased with advancing age. Adding sodium selenate to increase the total nonradioactive Se of human milk, bovine milk (endogenous plus the added selenium) did not affect the absorption of either [75Se]selenomethionine or [75Se]selenite.

Aging↗