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PubMed2006

Meat protein fractions enhance nonheme iron absorption in humans.

The nature of the enhancing effect of muscle tissue on nonheme iron absorption in humans is unclear but thought to be related to muscle proteins. We conducted radioiron absorption studies to compare iron absorption from proteins isolated from beef and chicken muscle with that from freeze-dried beef and chicken muscle and from egg albumin. All meals contained an equivalent amount of protein as part of a semisynthetic liquid formula. Freeze-dried beef and chicken muscle increased iron absorption 180% (P < 0.001) and 100% (P < 0.001), respectively, relative to egg albumin. When added to the meal at an equivalent protein level (15 g), the isolated beef protein and the isolated heme-free beef protein with 94 and 98% protein content, respectively, increased iron absorption to the same extent as the native beef muscle. Similarly, when added to the meal at an equivalent protein level (30 g), isolated chicken muscle protein (94% protein) increased iron absorption similarly to native chicken muscle. Iron absorption from the meal containing the isolated heme-free chicken protein, however, was 120% (P < 0.01) greater than from the meal containing freeze-dried chicken muscle, indicating that a nonprotein component of muscle tissue with iron-binding potential may have been removed or concentrated by the protein extraction and separation procedures. Our results support the hypothesis that the enhancing effect of muscle tissue on iron absorption is mainly protein related but indicate that other factors may also play a role.

Absorption↗
PubMed2006

Chili, but not turmeric, inhibits iron absorption in young women from an iron-fortified composite meal.

Chili and turmeric are common spices in indigenous diets in tropical regions. Being rich in phenolic compounds, they would be expected to bind iron (Fe)(3) in the intestine and inhibit Fe absorption in humans. Three experiments were conducted in healthy young women (n = 10/study) to assess the effect of chili and turmeric on Fe absorption from a rice-based meal containing vegetables and iron fortified fish sauce in vivo. Iron absorption was determined by erythrocyte incorporation of stable isotope labels ((57)Fe/(58)Fe) using a randomized crossover design. Addition of freeze-dried chili (4.2 g dry powder, 25 mg polyphenols as gallic acid equivalents) reduced Fe absorption from the meal by 38% (6.0% with chili vs. 9.7% without chili, P = 0.0017). Turmeric (0.5 g dry powder, 50 mg polyphenols as gallic acid equivalents) did not inhibit iron absorption (P = 0.91). A possible effect of chili on gastric acid secretion was indirectly assessed by comparing Fe absorption from acid soluble [(57)Fe]-ferric pyrophosphate relative to water soluble [(58)Fe]-ferrous sulfate from the same meal in the presence and absence of chili. Chili did not enhance gastric acid secretion. Relative Fe bioavailability of ferric pyrophosphate was 5.4% in presence of chili and 6.4% in absence of chili (P = 0.47). Despite the much higher amount of phenolics in the turmeric meal, it did not affect iron absorption. We conclude that both phenol quality and quantity determine the inhibitory effect of phenolic compounds on iron absorption.

Adult↗
PubMed2006

Iron deficiency, but not anemia, upregulates iron absorption in breast-fed peruvian infants.

Iron absorption in adults is regulated by homeostatic mechanisms that decrease absorption when iron status is high. There are few data, however, regarding the existence of a similar homeostatic regulation in infants. We studied 2 groups of human milk-fed infants using (57)Fe (given as ferrous sulfate without any milk) and (58)Fe (given at the time of a breast-milk feeding) stable isotopes to determine whether healthy infants at risk for iron deficiency would regulate their iron absorption based on their iron status. We studied 20 Peruvian infants at 5-6 mo of age and 18 infants at 9-10 mo of age. We found no effect of infant hemoglobin concentration on iron absorption with 5-6 mo-old infants absorbing 19.2 +/- 2.1% and 9- to 10-mo-old infants absorbing 25.8 +/- 2.6% of the (57)Fe dose. For (58)Fe, 5- to 6-mo-old infants absorbed 42.6 +/- 5.0% and 9 to 10-mo-old infants absorbed 51.9 +/- 10.3%. Following log transformation, iron absorption from (57)Fe (r = -0.61, P = < 0.001) and (58)Fe (r = -0.61, P = < 0.001) were inversely correlated to serum ferritin (S-Ft). For both the (57)Fe and (58)Fe doses, infants with S-Ft <12 mg/L (n = 11) had significantly higher iron absorption than those with S-Ft >12 mg/L. We concluded that iron absorption in infants is related to iron status as assessed by serum ferritin but not hemoglobin concentration. Infants with low iron status upregulate iron absorption from breast milk at both 5-6 and 9-10 mo of age.

Absorption↗
PubMed2007

A mathematical model of zinc absorption in humans as a function of dietary zinc and phytate.

The quantities of zinc and phytate in the diet are the primary factors determining zinc absorption. A mathematical model of zinc absorption as a function of dietary zinc and phytate can be used to predict dietary zinc requirements and, potentially, enhance our understanding of zinc absorption. Our goal was to develop a model of practical and informative value based on fundamental knowledge of the zinc absorption process and then fit the model to selected published data to assess its validity and estimate parameter values. A model of moderate mathematical complexity relating total zinc absorption to total dietary zinc and total dietary phytate was derived and fit to 21 mean data from whole day absorption studies using nonlinear regression analysis. Model validity, goodness of fit, satisfaction of regression assumptions, and quality of the parameter estimates were evaluated using standard statistical criteria. The fit had an R(2) of 0.82. The residuals were found to exhibit a normal distribution, constant variance, and independence. The parameters of the model, A(MAX), K(R), and K(P), were estimated to have values of 0.13, 0.10, and 1.2 mmol/d, respectively. Several of these estimates had wide CI attributable in part to the small number and the scatter of the data. The model was judged to be valid and of immediate value for studying and predicting absorption. A version of the model incorporating a passive absorption mechanism was not supported by the available data.

Humans↗
PubMed1998

Iron absorption in erythropoietin-treated haemodialysis patients: effects of iron availability, inflammation and aluminium.

BACKGROUND: The response to recombinant human erythropoietin (rHuEpo) is determined primarily by the availability of iron. In contrast to i.v., iron, oral iron supplementation is often insufficient for an optimal response. METHOD: We studied iron absorption and the effects of iron status, aluminium status and inflammation in 19 chronic haemodialysis patients on maintenance rHuEpo therapy. Iron mucosal uptake after 24 h, iron retention after 2 weeks and mucosal transfer of iron were determined with a whole-body counter using an oral dose 59Fe. Iron absorption was measured once without, and once after the ingestion of 2 g aluminium hydroxide. RESULTS: On the basis of transferrin saturation, two groups of dialysis patients were distinguished: a group with a functional iron deficiency (n = 9), and an iron-replete group (n = 10). In the iron-deficient dialysis patients group, mucosal uptake, mucosal transfer, and iron retention were 49.9% +/- 29.4, 0.73 +/- 0.29, and 41.6% +/- 32.2, being significantly lower than in a non-uraemic iron deficient population (P < 0.01, P < 0.05, P < 0.01 respectively). In the iron-replete dialysis patients group, mucosal uptake, mucosal transfer, and iron retention were 20.0 +/- 12.3, 0.59 +/- 0.18, and 11.1 +/- 6.7, mucosal uptake and iron retention being lower than in a normal iron-replete population (P < 0.0005 and P < 0.003 respectively). Dialysis patients with high C-reactive protein (CRP) values showed lower iron absorption. Iron absorption data correlated significantly with transferrin saturation and CRP in the iron-deficient group, and with serum ferritin in the iron-replete group. Iron absorption decreased after an aluminium hydroxide challenge in the iron-deficient patients to the lower levels of the iron-replete subjects. Body aluminium stores, estimated by the desferrioxamine test, did not correlate with parameters of iron absorption. CONCLUSION: The absorption of iron in dialysis patients is decreased in haemodialysis patients, which may, at least in part, be due to inflammation. Aluminium ingestion further reduces absorption in functional iron-deficient patients.

Absorption↗
PubMed2005

A physiologically based pharmacokinetic model of organophosphate dermal absorption.

The rate and extent of dermal absorption are important in the analysis of risk from dermal exposure to toxic chemicals and for the development of topically applied drugs, barriers, insect repellents, and cosmetics. In vitro flow-through cells offer a convenient method for the study of dermal absorption that is relevant to the initial processes of dermal absorption. This study describes a physiologically based pharmacokinetic (PBPK) model developed to simulate the absorption of organophosphate pesticides, such as parathion, fenthion, and methyl parathion through porcine skin with flow-through cells. Parameters related to the structure of the stratum corneum and solvent evaporation rates were independently estimated. Three parameters were optimized based on experimental dermal absorption data, including solvent evaporation rate, diffusivity, and a mass transfer factor. Diffusion cell studies were conducted to validate the model under a variety of conditions, including different dose ranges (6.3-106.9 microg/cm2 for parathion; 0.8-23.6 microg/cm2 for fenthion; 1.6-39.3 microg/cm2 for methyl parathion), different solvents (ethanol, 2-propanol and acetone), different solvent volumes (5-120 microl for ethanol; 20-80 microl for 2-propanol and acetone), occlusion versus open to atmosphere dosing, and corneocyte removal by tape-stripping. The study demonstrated the utility of PBPK models for studying dermal absorption, which can be useful as explanatory and predictive tools that may be used for in silico hypotheses generation and limited hypotheses testing. The similarity between the overall shapes of the experimental and model-predicted flux/time curves and the successful simulation of altered system conditions for this series of small, lipophilic compounds indicated that the absorption processes that were described in the model successfully simulated important aspects of dermal absorption in flow-through cells. These data have direct relevance to topical organophosphate pesticide risk assessments.

Administration, Cutaneous↗
PubMed1996

Biphasic drug absorption from the epidural space of the dog may limit the utility of a slow release medium molecular weight hyaluronic acid-lidocaine ionic complex formulation.

Previous epidural studies conducted in rabbits have described a viscous lidocaine-hyaluronate formulation (L-HA) that prolonged the duration of sensory blockade twofold and decreased the rate of drug absorption fourfold relative to a solution formulation. As further evaluation of the L-HA formulation required studies in a larger animal that more closely reflected the characteristic absorption kinetics observed in humans, a conscious dog model was used to functionally and kinetically evaluate the viscous formulation relative to lidocaine solution. In terms of the measured pharmacodynamic end point (loss of weight-bearing ability in hind legs), epidural administration of the L-HA formulation did not prolong the duration of action relative to lidocaine solution in spite of a markedly altered pharmacokinetic profile. For example, administration of L-HA reduced the mean plasma lidocaine Cmax value approximately 50% and increased the Tmax value approximately fivefold relative to lidocaine solution. However, the viscous L-HA formulation did cause a significant prolongation in the latency of onset (P < 0.001) relative to lidocaine solution. The dog exhibited "flip-flop" pharmacokinetics and absorption was biphasic after epidural administration of lidocaine solution (apparent t1/2 of the fast and slow absorption phases were 4 min and 131 min, respectively). The L-HA formulation markedly altered the absorption kinetics such that a single, slow absorption phase was evident (apparent t1/2 of 56 min), although this rate was more rapid than the slow phase observed after lidocaine solution. It is possible that the inability of the hyaluronate-based formulation to further reduce the magnitude of the slow absorption phase resulted in the failure to prolong the duration of action. These data highlight the need to carefully consider the absorption kinetics and pharmacokinetic characteristics of the animal models chosen to evaluate new formulation of epidurally administered local anesthetics.

Absorption↗
PubMed1991

Selenium absorption and retention by very-low-birth-weight infants: studies with the extrinsic stable isotope tag 74Se.

Measurements of dietary selenium absorption and retention were obtained after administration of a single dose of the extrinsic stable isotope tag 74Se in 20 appropriate for gestational age premature infants with birth weights between 720 and 1,630 g and gestational ages between 26 and 33 weeks. Infants were assigned randomly to receive a standard premature formula (1.34 microgram of Se/dl) or a selenium-supplemented version of that formula (2.03 micrograms of Se/dl). Each study consisted of one feeding that had been extrinsically labeled with 74Se (1.03 microgram/kg) and a timed stool and urine collection. The percent 74Se absorption was 91.2 +/- 5.4% (mean +/- SD) from the standard formula and 86.2 +/- 3.0% from the selenium-supplemented formula (p less than 0.05), but the percent of the absorbed 74Se retained was not different, i.e., 96.6 +/- 2.1% and 95.0 +/- 2.8%, respectively. The percent net absorption and net retention were also not different between the standard and selenium-supplemented formulas; net absorption was 72.7 +/- 18.1% vs. 67.8 +/- 18.8% and net retention was 57.2 +/- 17.6% vs. 53.3 +/- 20.2%, respectively. The percent 74Se absorption and true selenium absorption were significantly correlated with the percent net selenium absorption and net selenium absorption, respectively. We conclude that an extrinsically administered dose of 74Se can be used to study selenium nutrition in growing premature infants.

Birth Weight↗
PubMed2005

Role of interleukin-6 in hypoxic regulation of intestinal iron absorption.

The regulation of intestinal iron absorption is not fully understood. Hepcidin, a liver-produced peptide, has recently been identified as a negative regulator of iron absorption in various conditions associated with altered iron metabolism (e.g. inflammation, anaemia, hypoxia). It is not clear whether these perturbants share a common signalling pathway. In this study, the importance of the cytokine interleukin-6 (IL-6) was investigated in the hypoxic mouse model. Hypoxia was associated with increased levels of circulating IL-6, decreased liver hepcidin mRNA and increased iron absorption (especially MT). A significant positive correlation existed between the total iron uptake and IL-6 levels in circulation. IL-6 per se, though inducing hepcidin mRNA, failed to affect basal iron absorption. The adaptive response to absorption following the hypoxic exposure was, however, more prominent if mice had been treated concurrently with IL-6. This enhancement in absorption occurred even though hepcidin mRNA was not significantly changed. Similar prominent responses were seen with both human and mouse IL-6. Anti-IL-6 antiserum normalised iron absorption in mice exposed to hypoxia, because of a reduction in the MT. These data indicate that IL-6 can influence iron absorption (especially MT) during the hypoxic exposure, but via a mechanism independent of hepcidin.

Animals↗
PubMedDate not supplied

Intestinal absorption of lithocholate and its sulfate and glucuronide in rats.

The absorption of lithocholate and its sulfate and glucuronide in rat jejunum and terminal ileum was studied. Tracer amounts of radiolabelled bile acids were administered to the ligated intestinal segments, and their absorption was monitored by biliary excretion through a bile duct catheter. Absorption of lithocholate was faster in the terminal ileum than in the jejunum. Although the sulfation reduced lithocholate absorption in the jejunum, it did not affect lithocholate absorption in the terminal ileum. This was due to the Na+-dependency of ileal absorption of lithocholate-sulfate assessed by perfusion studies. In contrast, the glucuronidation markedly reduced lithocholate absorption both in the jejunum and the terminal ileum. These findings indicate that the glucuronidation is more effective than sulfation in detoxifying lithocholate as far as the prevention of its intestinal absorption is concerned.

Absorption↗
PubMed1992

Persistent diarrhoea: factors affecting absorption and clinical prognosis during management with a rice-based diet.

Twenty-six persistent diarrhoea patients aged 4 to 18 months were treated with a diet prepared with rice powder, soya oil, glucose, egg white and water. Absorption of macronutrients was estimated in a 72 h balance study and clinical response was examined during one week of dietary treatment. Nutrient absorption was compared with that of 25 healthy age-matched controls treated with the same diet. Twenty-one patients (81%) recovered from diarrhoea within seven days. Absorption of nutrients was significantly reduced among the persistent diarrhoea patients. More malnourished patients had a significantly reduced absorption of nutrients except carbohydrate and an increased severity and longer duration of diarrhoea. Total gut transit time had significant association with nutrient absorption in the persistent diarrhoea patients. The period of recovery negatively correlated with coefficient of absorption and positively with initial stool weight. Failure to recover was associated with severity of diarrhoea and systemic infection. The study indicates that nutrient absorption is significantly reduced in patients with persistent diarrhoea and nutritional status, and that initial purging rate and intestinal hurry are significantly related to the prognosis and nutrient absorption.

Arm↗
PubMed1991

Absorption of iron from iron succinyl-protein complexes by mouse small intestine.

The absorption of iron from iron succinyl-protein complexes was investigated in mice. 59Fe-labelled succinyl-casein and -albumin complexes, [59Fe]ferritin and 59FeSO4, at doses of 20 or 200 micrograms of iron, were administered orally to normal mice or mice with absorption enhanced by chronic hypoxia. 59Fe from iron succinyl-protein was well absorbed in normal mice (greater than 10% of dose) and showed enhanced absorption in hypoxic mice (greater than 40% of dose). Intestinal uptake was predominantly by the duodenum for all compounds studied. In-vivo absorption of 59Fe from an iron succinyl-protein complex was studied using tied-off segments of mouse duodenum, jejunum or ileum of normal or hypoxic mice. Incubation for up to 15 min in duodenum or 60 min in ileum showed very little absorption of 59Fe. No enhancement of absorption was seen in hypoxic mice. It was concluded that absorption of the intact iron succinyl-protein complex cannot explain absorption seen after oral dosing.

Animals↗
PubMed1993

Studies on an oral iron chelator: 1,2-dimethyl-3-hydroxy-pyrid-4-one (DMHP). Mechanism of intestinal absorption in rabbits.

Over the last 30 years, desferrioxamine has been the only iron chelator in clinical use. This chelator is expensive and must be given by injection. A new class of chelators, namely 1-alkyl-2-methyl-3-hydroxypyrid-4-ones, have been shown to be orally effective. Using 1,2 dimethyl-3-hydroxy-pyrid-4-one (DMHP), we have carried out a study to clarify the mechanism of intestinal absorption of this new class of drug, using an in-situ system of the intestine from rabbit. The major site of DMHP absorption is in the intestine and is linear with increasing drug concentration. DMHP absorption per unit length of jejunum and ileum is similar; however, due to the larger surface area of jejunum, the absorption by ileum segment is more effective per unit surface. L-Proline, L-tryptophan (amino acids), 2-deoxyglucose, and sodium iodoacetate (metabolic inhibitors) have no effect on DMHP absorption, but L-phenylalanine, an amino acid with a 6-member carbon ring, significantly inhibits the DMHP absorption from the intestinal segment. We conclude that the mechanism of DMHP absorption in the intestine is mainly by simple passive diffusion based on the linear relationship found between drug concentration and absorption. However, the inhibitive effect of L-phenylalanine suggests that the co-existence of a facilitated uptake cannot be ruled out.

Administration, Oral↗
PubMed1986

Anion control of sodium absorption in the colon.

The regulatory functions of anions in colonic absorption of sodium are unknown. Absorption of sodium ions was assessed with chloride, butyrate, nitrite, sulphate and oxalate anions in segments of proximal/distal colon and in defunctioned colon. Efficiency of sodium absorption was related to availability of CO2 in mucosal cells: CO2 availability was enhanced (P less than 0.01) by sodium nitrite or diminished (P less than 0.01) in defunctioned colon. Sodium nitrite stimulated absorption of sodium in the distal colon where bicarbonate secretion predominated and n-butyrate stimulated absorption of sodium in the proximal colon where hydrogen ion secretion predominated. Sodium absorption was very significantly diminished (P less than 0.01) in defunctioned colon. Results indicate that sodium absorption in the colon is both a double anion exchange system as well as cation/anion co-transport. Anions act differently on sodium absorption along the length of the colon and prolonged lack of anions plays a part in sodium malabsorption of the defunctioned colon.

Absorption↗
PubMed1969

The influence of specific chemical factors in the solvent on the absorption of macromolecular substances from the small intestine of the new-born calf.

1. The absorption, without change, of [(131)I] and [(125)I]solutes of high molecular weight after duodenal infusion has been measured in anaesthetized calves less than 20 hr old by analysis of lymph collected from the thoracic or intestinal duct.2. Factors present in boiled bovine colostrum whey known to be necessary for the rapid absorption of [(131)I]bovine serum gamma-globulin have now been shown to accelerate the passage of [(131)I]polyvinyl pyrrolidone (PVP) of mean mol. wt. 160,000 (K.60) into the lymph in a comparable manner.3. [(131)I]PVP K.30 (mean mol. wt. 40,000) and [(131)I]human serum albumin could be absorbed to some degree in the absence of solvent factors necessary for the absorption of solutes of higher mol. wt. and a large proportion of the solute thus absorbed passed directly into the portal capillaries.4. Lactate and pyruvate and salts of certain lower volatile fatty acids resemble factors in colostrum whey in their facilitation of the absorption of both gamma-globulin and PVP K.60: these active compounds were not however found in colostrum in significant quantities.5. Potassium isobutyrate was the most effective of the compounds tested and at concentrations of 56.7 m-mole/l. generally accelerated absorption to a greater degree than did colostrum whey itself.6. Absorption of both gamma-globulin and PVP K.60 from colostrum whey was characterized by a profuse flow of lymph containing relatively low concentrations of labelled solute. In contrast, when these solutes were fed in solutions containing simple compounds such as potassium isobutyrate they appeared in very high concentrations in the lymph, the flow of which remained relatively scant.7. When [(125)I]PVP was administered in water, little was absorbed. If, however, such an infusion was followed 3 hr later by a duodenal infusion of colostrum, [(125)I]PVP passed into the lymph almost immediately. This response was too rapid for the colostrum to have reached the absorbing cells in the terminal ileum.8. Intravenous infusions of L+lactate have been found to facilitate the absorption of [(125)I]PVP K.60 introduced into the duodenum in water. This indicates that some of the solvent factors which accelerate absorption may reach the terminal ileum via the blood vascular system after they themselves have been absorbed from the upper small intestine.

Animals↗
PubMed1973

Effect of previous dietary history of calcium intake on the skeleton and calcium absorption in the rat.

1. Rats were fed either a high or a low calcium diet for 6 weeks. Thereafter all were given the low calcium diet, and the time during which differences persisted between the two groups in apparent absorption of calcium and urinary excretion of calcium has been studied. The apparent absorption of calcium is the same in the two groups after 15 days but the differences in urinary excretion of calcium persist longer.2. Faecal endogenous calcium and true absorption of calcium have been measured by an isotope dilution technique. The fall in apparent absorption of calcium seen in rats fed a high calcium diet is in part due to a fall in true absorption. Faecal endogenous calcium is also increased in these animals.3. The amount of calcium and phosphate in the bones is increased by feeding a high calcium diet and decreased by feeding a very low phosphate diet. Femur, humerus, caudal vertebrae and calvaria are equally affected by the different diets.4. There are strong inverse correlations between absorption of calcium and the percentage of calcium in the bones. This suggests that absorption of calcium may be regulated by the degree of bone mineralization.5. Rats were fed diets with different calcium phosphate ratios for 6 weeks. Thereafter all were given a low calcium diet with a calcium: phosphorous ratio of 1 and absorption and urinary excretion of calcium were studied. The effects of the different diets may be explained by their effect on calcium status and bone mineralization.

Animals↗
PubMed1977

Calcium absorption in diphosphonate-treated rats: effect of parathyroid function, dietary calcium and phosphorus.

1. The role of parathyroid hormone (PTH) and 1, 25-dihydroxy-cholecalciferol (1,25-(OH)2D3) in modulation of intestinal Ca absorption was studied in rats, using disodium ethane-1-hydroxy-1,1-diphosphonate (EHDP), which is known to reduce 1,25-(OH)2D3 formation. 2. EHDP decreased intestinal Ca absorption. This effect could be abolished by small amounts of 1,25-(OH)2D3, whereas even large doses of PTH were ineffective. EHDP also decreased Ca absorption in thyroparathyroidectomized (TPTX) rats. Therefore the effect of EHDP on 1,25-(OH)2D3 production is unlikely to be mediated through PTH. 3. The correction by PTH of the decreased Ca absorption in TPTX rats was inhibited by EHDP. Since EHDP inhibits formation of 1,25-(OH)2D3 the effect of PTH on Ca absorption is likely to be mediated through this vitamin D3 metabolite. 4. In normal rats both a low Ca and a low P diet stimulated Ca absorption. In EHDP-treated intact rats low Ca still stimulated Ca absorption, whereas the effect of low P abolished. This indicates that low Ca and low P diets affect Ca absorption through different mechanisms. 5. Intestinal adaptation to a low Ca diet was still observed in EHDP-treated TPTX rats. Thus, in the rat, intestinal adaptation to low Ca diet can occur without PTH.

Animals↗
PubMed1980

Absorption by the colon during prolonged infusions in conscious, unrestrained rats.

1. Colonic absorption was studied in conscious, unrestrained rats during prolonged infusions through implanted cannulae. During infusion of predominantly NaCl-containing solution at rates up to 0.7 ml h-1 per 100 g body wt., absorption of fluid and Na increased considerably without significant change of transmucosal p.d.; diarrhoea did not occur. 2. Exclusion of the distal colon by colostomy showed that the proximal part of the colon was chiefly responsible for the increased absorption and inspection during the infusion showed it to be much dilated. Removal of the caecum showed that it contributed considerably to absorption by the proximal part. The distal colon influenced Na concentration in the faeces but absorbed little volume while direct infusion into this region rapidly produced diarrhoea. 3. The addition of Na deoxycholate (5 mmol/l) to the infusion solution impaired absorption provoking diarrhoea with mucus loss; there was no evidence that fluid secretion was stimulated. Substitution of SO4 for Cl in the infused solution produced only small changes of transmucosal p.d. but considerably impaired absorption and diarrhoea resulted. 4. The findings indicate that the proximal colon and caecum possess a considerable potential for increasing fluid and Na absorption and suggest the possibility that a neutral Na-Cl coupled absorptive mechanism is stimulated by loading the colon with fluid and NaCl.

Animals↗