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PubMed1997

Native corn starch versus either cellulose or glucose in the diet and the effects on apparent magnesium absorption in goats.

The objective of this study was to determine whether dietary glucose or starch would reduce the inhibitory effect of high K intake on Mg absorption in ruminants. In a 6 x 6 Latin square design, six goats were fed diets with or without added KHCO3 containing either cellulose, glucose, or native corn starch. The K concentrations of the diets were 7.8 or 34.0 g or K/kg of dry matter, and carbohydrates were incorporated so that their concentrations were identical on a glucose equivalent basis (331 g of glucose/kg of dry matter). The intake of extra K significantly reduced apparent Mg absorption from 29.8 to 22.1% on average. Glucose, instead of cellulose, in the diet did not affect Mg absorption. Replacement of dietary cellulose by corn starch enhanced the mean efficiency of Mg absorption from 21.8 to 30.9%. Starch versus glucose increased Mg absorption by 5.8 percentage units. No statistically significant interaction was observed between the type of carbohydrate and the amount of K in the diet with regard to Mg absorption. This study showed that the inhibitory effect of dietary KHCO3 on Mg absorption in goats was fully counteracted by the replacement of cellulose with starch in the diet. Possible changes in the pH of ruminal fluid might have mediated the dietary effects on Mg absorption.

Absorption↗
PubMed1988

Intestinal absorption of riboflavin, studied by an in situ circulation system using radioactive analogues.

The intestinal absorption of riboflavin was studied using radioactive riboflavin and its analogues 8-demethylriboflavin, 3-methylriboflavin, 5'-deoxyriboflavin, 2'-deoxyriboflavin, 7,8-dimethyl-10-hydroxyethylisoalloxazine, lumiflavin, lumichrome, and riboflavin-5'-monosulfate, which were synthesized with high specific radioactivity. A specific absorption of riboflavin at dietary concentrations was confirmed using an in situ circulation system. The relation between the chemical structure of flavins and the absorption mechanism was studied using this system. The 8-demethylriboflavin, an analogue modified at benzene moiety of the isoalloxazine ring, was absorbed in a similar way to riboflavin, by dual kinetics: by a process specific for riboflavin at dietary concentrations and by simple diffusion (nonspecific absorption) predominating at higher concentrations (over 100 microM). However, 3-methylriboflavin and analogues modified at the ribityl group, including 5'-deoxyriboflavin, were absorbed only via simple diffusion even at dietary concentrations. Many flavins examined, except for 3-isobutylriboflavin, 3-carboxymethylriboflavin, lumichrome, and riboflavin-5'-monosulfate, interfered with the specific absorption of riboflavin. It was concluded from these results that one of the specific absorption processes for riboflavin is a phosphorylation-dephosphorylation process. Four water-soluble vitamins did not interfere with the specific absorption of riboflavin, indicating that these vitamins do not share a common specific absorption pathway with riboflavin.

Animals↗
PubMed1991

Comparison of absorption of erythorbic acid and ascorbic acid in guinea pig small intestine.

Both the ascorbic acid (AsA) and erythorbic acid (ErA) absorption in the small intestine of guinea pigs were determined by the perfusion of the small intestine using isotonic phosphate buffer recycled in situ. The absorption rate of AsA in the small intestine of guinea pigs was higher than that of ErA; however, Km of AsA absorption was lower than that of ErA in normal guinea pigs. In AsA-deficient guinea pigs, the absorption rates of both AsA and ErA were higher than those in normal ones. The absorption of AsA and ErA in the small intestine of guinea pigs was inhibited by ouabain. Furthermore, AsA and ErA inhibited each other's absorption. Based on the results, the net amount of the absorbed ErA in the small intestine may be lower than that of AsA, and ErA absorption mechanism seemed to be similar to that of AsA. The absorption rate of both AsA and ErA in the small intestine of guinea pig might be dependent on the AsA level in the tissues.

Animals↗
PubMed1998

Effect of L-lactic acid on calcium absorption in rats fed omeprazole.

We examined the effect of L-lactic acid on calcium absorption in male Wistar rats made achlorhydric by dietary omeprazole, a proton pump inhibitor. The dietary omeprazole intake (0.03 g/100 g of diet) increased the gastric pH and decreased the apparent calcium absorption ratio. Dietary famotidine (0.03 g/100 g of diet), an H2-receptor antagonist, and lower doses of omeprazole (0.005 or 0.01 g/100 g of diet) did not affect the gastric pH or the calcium absorption. In a second experiment, dietary lactic acid (0.5, 1.0, or 2.5 g/100 g of diet) increased the intestinal calcium absorption dose dependently in rats fed omeprazole (0.03 g/100 g of diet). The gastric pH was significantly decreased only in the rats fed higher doses of lactic acid (1.0, or 2.5 g/100 g of diet). In a third experiment, a dietary sour milk beverage containing lactic acid (0.5 g/100 g of diet) increased the intestinal calcium absorption, but did not affect the gastric pH in rats fed omeprazole (0.03 g/100 g of diet). Although the significance of gastric acid in terms of overall calcium absorption is not known, under the present experimental conditions, the inhibition of gastric acid secretion by dietary omeprazole decreased the apparent calcium absorption, and the dietary lactic acid prevented the calcium absorption in rats fed omeprazole.

Animals↗
PubMed1976

Effects of experimental diabetes on intestinal strontium absorption in the rat.

Control and streptozotocin diabetic rats were studied at 5 and 12 days after induction of diabetes. Strontium absorption was measured by in situ perfusion of duodenum and ileum. Duodenal absorptive capacity (absorption per unit length) and absorptive specific activity (absorption per gram of dry weight mucosa) were depressed. Depression was present both at 5 days, when mucosal growth is similar in controls and diabetics, and at 12 days, when mucosal growth is 50% greater in diabetics. Effects of diabetes on ileal absorption were minimal in comparison with effects on duodenum. This depression of duodenal strontium absorption in the diabetic rat is analogous to effects of diabetes on calcium absorption and may be mediated by abnormal vitamin D metabolism.

Animals↗
PubMed1983

Effect of dietary fiber on absorption of B-6 vitamers in a rat jejunal perfusion study.

Previous research has indicated that dietary fiber may affect the absorption and utilization of certain nutrients. To determine the effect of certain fiber materials on the absorption of B-6 vitamers, jejunal segments from young male adult rats were perfused in situ with a control solution containing 0.02 mM pyridoxine (PN), 0.02 mM pyridoxal (PL), and 0.02 mM pyridoxamine (PM), followed by a test solution containing the same vitamin B-6 mixture and one of five fiber-rich test materials (cellulose, pectin, lignin, homogenized fresh carrot, or carrot homogenized after 10 min boiling) added at a concentration of 1-3%. The mean absorption rates of PL, PN, and PM from the control solution were, respectively, 3.66 +/- 0.23, 2.06 +/- 0.23, and 1.74 +/- 0.37 nmole/min/20 cm jejunal segment. There were no significant differences between the absorption rates of B-6 vitamers from control and test solutions containing cellulose, pectin, and lignin. The absorption rates of PM and PL were significantly depressed (P less than 0.05 and P less than 0.01, respectively) by the presence of fresh or cooked carrot. The absorption rate of PN in presence of cooked carrot was also decreased relative to the control value but the difference was only marginally significant (P less than 0.10). When the concentration of fresh carrot in the test solution was increased to 10% by weight and the perfusion rate was decreased from 1.91 to 0.49 ml/min in a second perfusion experiment, there was a significant increase in variability and the differences between absorption rates of the B-6 vitamers in control and test solutions were not statistically significant. The limited evidence of adverse effect of carrot on absorption of vitamin B-6 suggested the need for further clarification of the influence of dietary fiber in an unrefined state on the bioavailability of vitamin B-6.

Animals↗
PubMed1987

Intestinal absorption of copper: effect of sodium.

The mechanisms of copper (Cu) absorption from the small intestinal lumen are poorly understood. In this study we investigated the role of sodium (Na) during the removal of Cu from the lumen of jejunal and ileal segments, using an in situ perfusion procedure in the anesthetized rat. Intestinal absorption of Cu from a 31 microM solution was highest in the presence of an isotonic concentration of NaCl, as compared to solutions containing either glycerol (GRL) or N-methyl-D-glucamine (NMG) as osmotic agents. In the jejunum, mean +/- SEM Cu absorption rates in the presence of the following solutes were: with NaCl, 57.5 +/- 10.5 pmole/min X cm; with GRL, 13.3 +/- 14.7 (P less than 0.05); with NMG, 18.4 +/- 10.1 (P less than 0.05). In the ileum, copper absorption in the presence of NaCl was 64.4 +/- 9.6; with GRL, 24.3 +/- 10.1 (P less than 0.01); with NMG, 15.8 +/- 3.7 (P less than 0.001). Kinetic analysis of the carrier-mediated component of Cu absorption in rat jejunum yielded a Vmax = 47.5 pmole/min X cm and an apparent Kt = 21 microM. The diffusion coefficient was calculated to be 1.4 X 10(-5) cm2/sec. The absorption of Cu was independent of net water absorption, which was highest in the presence of GRL and abolished and reversed into secretion by NMG. The data obtained are indicative of a significant role of Na in the small intestinal transport of Cu, in vivo, although not directly related to unidirectional water fluxes. The cation specificity of Na in this process remains to be elucidated, although the results support earlier studies which postulated that mediated transport may constitute a major component of Cu absorption in the mammalian small intestine.

Absorption↗
PubMed1997

Cellulose derivatives and intestinal absorption of water and electrolytes: potential role in oral rehydration solutions.

The physicochemical and structural characteristics of several types of carboxymethylcellulose (CMC) and of methylcellulose (MC) were examined in relation to their capacity to modify water and sodium absorption in oral rehydration solutions (ORS) at various concentrations, using a jejunal perfusion procedure in rats. Comparison of intrinsic low-viscosity CMC of various degrees of substitution (DS) revealed that net water absorption increased as the DS was augmented. A stimulatory effect on sodium absorption occurred only at a low (2.5 g/l) CMC concentration. With products of medium DS, stimulation of net water and sodium absorption was observed only with low-viscosity CMC at 2.5 g/l, but not at 5.0 g/l. In perfusions with CMC of medium and high DS there was a reduction of water and sodium absorption, ultimately resulting in net sodium secretion with 5.0 g/l high-DS CMC. MC perfused at 5.0 or 10.0 g/l reduced net water absorption and reversed sodium transport from absorptive to secretory status. These results show that while low-viscosity-grade, low-DS CMC in low concentrations may facilitate solute uptake and concurrent water absorption from ORS by the jejunum, high intrinsic viscosity and possible chemical interaction of solutes with the modified celluloses tend to block water uptake and produce fluid stasis and electrolyte secretion. Thus, the data suggest that only certain types of CMC may be proabsorptive when added to ORS, while high-viscosity and high-DS CMC or MC induce electrolyte malabsorption and eventual catharsis.

Animals↗
PubMed2003

Estimating cadmium absorption rate in digestive organs calculated from information of studies on cadmium conducted in Japan.

The absorption rate of cadmium (Cd) in the digestive organs is reported to be 0.5-8% in Friberg's textbook. This value was obtained from experimental studies. The object of the present study is to obtain the value from the Cd intake amount by ingestion, the Cd absorption amount by respiration and smoking, and the total Cd absorption amount calculated from the Cd accumulation amount in organs reported in articles including not only experimental but also epidemiologic studies conducted in Japan. The oral intake amounts of Cd in Japan were obtained from a published article to be 48 micrograms/day for males in the 1970s. The total Cd absorption amount that was calculated from the Cd accumulation amount in organs of 223 male subjects autopsied following sudden death was found to be 6.8 micrograms/day for male adults in the 1970s. The Cd exposure before the 1970s reflected the Cd absorption amount calculated from the Cd accumulation amount in the 1970s. The Cd absorption amount by respiration and smoking for males in the 1960s was 1.0 microgram/day, and the difference of 5.8 micrograms/day between the above two corresponds to the Cd absorption amount in digestive organs before the 1970s. The rice intake amount for Japanese in 1955-1965 was reported to be about 1.4 times as much as that in 1975. Therefore the Cd absorption rate in digestive organs was estimated to be about 10% from these values, assuming that most of the change in Cd intake from food is derived from the amount of rice eaten in Japan. This value is somewhat greater than the values published in the literature.

Absorption↗
PubMed1999

Neural modulation of cephalexin intestinal absorption through the di- and tripeptide brush border transporter of rat jejunum in vivo.

Intestinal absorption of beta-lactamine antibiotics (e.g., cefixime and cephalexin) has been shown to proceed through the dipeptide carrier system. In a previous study, nifedipine (NFP), an L-type calcium channel blocker, enhanced the absorption of cefixime in vivo but not in vitro, and it was suggested that neural mechanisms might be involved in the effect of NFP. The aim of the present study was to assess the involvement of the nervous system on the intestinal absorption of cephalexin (CFX). To investigate this, we used a single-pass jejunal perfusion technique in rats. NFP and diltiazem enhanced approximately 2-fold the plasma levels of CFX in treated rats versus untreated controls. NFP also increased approximately 2-fold the CFX level in portal plasma and increased urinary excretion of CFX, thus indicating that CFX did effectively increase CFX intestinal absorption. Perfusing high concentrations of dipeptides in the jejunal lumen competitively reduced CFX absorption and inhibited the enhancement of CFX absorption produced by NFP. Hexamethonium and lidocaine inhibited the effect of NFP, whereas atropine, capsaicin, clonidine, and isoproterenol enhanced CFX absorption by the same order of magnitude as NFP. Thus, complex neural networks can modulate the function of the intestinal di- and tripeptide transporter. Sympathetic noradrenergic fibers, intestinal sensory neurons, and nicotinic synapses are involved in the increase of CFX absorption produced by NFP.

ATP-Binding Cassette Transporters↗
PubMed1999

Hydrolysis-dependent absorption of disaccharides in the rat small intestine (chronic experiments and mathematical modeling).

In order to throw light on the mechanisms responsible for the enzyme-dependent absorption of disaccharides membrane hydrolysis of maltose and trehalose and the absorption of glucose (free and that derived from disaccharides) were studied in isolated loops (20 cm) of the rat small intestine in chronic experiments. The rates of glucose absorption were 0.26-0.81 micromol x min(-1) x cm(-1) when the loop was perfused with a 12.5 to 75.0 mmol/l free glucose solution, which is only insignificantly higher than the rates observed during perfusion with equivalent maltose solutions. The coupling coefficient (the ratio of glucose absorption rate to the rate of disaccharide hydrolysis) decreased from 0.90 to 0.60 with the increasing maltose concentrations in the infusate from 6.25 to 37.5 mmol/l, but remained unchanged (approximately 0.95) within the same range of trehalose concentrations. The permeability of the pre-epithelial barrier was equivalent to that of unstirred water layer of less than 40 microm thickness. Fluid absorption was within the range of 0.73-2.55 microl x min(-1) x cm(-1), and it showed a correlation with the rates of glucose absorption. The results agree with a model developed on the assumption that free glucose and that released from disaccharides share the same membrane transporters. It could be concluded that a close coupling of disaccharide hydrolysis with derived glucose absorption in chronic experiments is achieved mainly due to a high activity of glucose transporters, which are presumably not associated with membrane disaccharidases. The transcellular active transport is a predominant mechanism of disaccharide-derived glucose absorption under conditions close to physiological.

Absorption↗
PubMed2000

Influence of evaporation and solvent mixtures on the absorption of toluene and n-butanol in human skin in vitro.

The influence of forced ventilation on the percutaneous absorption of butanol and toluene was studied in vitro. Human skin was exposed to the neat solvents and the solvents in binary mixtures with each other and in ternary mixtures with chloroform:methanol. The exposure was either unventilated or ventilated with various flow rates. At the ventilated exposure the skin absorption of all solvents and solvent mixtures was markedly reduced compared to unventilated exposure. Exposure with solvent mixtures increased the amounts of solvent absorbed as well as absorption rates. The absorption of the butanol component was most influenced. Increase in absorption was 11 to 9 times depending on whether toluene or chloroform/methanol was cosolvent. There was also an interindividual variation of absorption rate, varying with a factor of 3.5 for toluene and 4.3 for n-butanol within the 3 skin donors used. Skin absorption of volatile organic solvents at continuous ventilated conditions is related to their volatility and to the ventilation rate.A sufficient workplace ventilation is an important occupational hygienic measure not only to reduce exposure via respiration but to reduce absorption via the skin of volatile compounds as well.

1-Butanol↗
PubMed1999

Ingestion of guar-gum hydrolysate partially restores calcium absorption in the large intestine lowered by suppression of gastric acid secretion in rats.

We examined the effects of feeding guar-gum hydrolysate (GGH), a highly fermentable form of dietary fibre with low viscosity, on Ca absorption in the small and large intestines in rats under conditions in which gastric acid secretion was suppressed by a proton pump inhibitor, omeprazole. We also examined the role of the caecum in influencing these effects. The study was designed in a 2 x 2 x 2 factorial arrangement with two diet (GGH-containing (50 g/kg diet) and GGH-free diets) groups, two injection (omeprazole and vehicle) groups and two operation (sham and caecectomy) groups. Apparent Ca absorption was lower in rats administered omeprazole (30 mg/kg body weight per d) for 8 d than in rats administered the vehicle. Ingestion of GGH led to partial restoration of Ca absorption decreased by omeprazole treatment. However, this increment in Ca absorption was not sufficient to meet requirements because the dietary Ca level (3.0 g/kg diet) was the minimum requirement for the intact rats. The small increment in Ca absorption caused by the GGH diet was completely abolished by caecectomy. Soluble Ca pools in the caecal and colonic contents were increased by feeding GGH, and the soluble Ca concentrations were much higher than the Kt values of the Ca active transport system in the large intestine or the serum Ca concentration. These findings suggest that Ca solubilization is not a limiting factor for Ca absorption in the large intestine. Apparent Mg absorption was clearly lower in caecectomized rats than in sham-operated rats, and higher in the GGH-fed groups than in the groups fed on the GGH-free diet, even in the case of caecectomized rats. We conclude that Ca absorption lowered by inhibition of gastric acid secretion is partially restored in rats fed with GGH, but the increment is not sufficient to meet requirements.

Animals↗
PubMed2000

Ingestion of the soluble dietary fibre, polydextrose, increases calcium absorption and bone mineralization in normal and total-gastrectomized rats.

We previously demonstrated that feeding a highly fermentable and water-soluble dietary fibre, guar-gum hydrolysate (GGH) increased intestinal absorption of insoluble Ca salts in total-gastrectomized rats. In the present study, we examined the effects of feeding a less fermentable and water-soluble fibre, polydextrose (PD), on Ca absorption and bone mineralization in the normal and total-gastrectomized rats in comparison with the effects of GGH. Apparent Ca absorption was severely lowered by gastrectomy, and PD feeding (50 g/kg diet) partially restored the reduction of Ca absorption similarly to GGH feeding (50 g/kg diet). PD feeding also increased the Ca absorption in normal rats, but not GGH feeding. Femur Ca concentration was reduced with gastrectomy. Feeding PD for 21 d increased the bone Ca concentration in both normal and gastrectomized rats, but GGH feeding did not. In rats fed PD, pH of the caecal contents was lower than in rats fed fibre-free and GGH diets; however, soluble Ca concentration in the caecal contents was not different between the diet groups. Short-chain fatty acid concentrations were much lower in the PD groups than in the GGH groups. We also examined in vitro Ca absorption by using everted sacs of the small intestine. Addition of PD to the serosal medium of the ileal sacs increased Ca absorption, but addition of GGH did not. These results suggest that the small intestine rather than the large intestine is responsible for the increase in Ca absorption in rats fed PD, and suggests that the mechanism for the increase by PD may be different from that by GGH.

Analysis of Variance↗
PubMed2001

Genetic factors at the enterocyte level account for variations in intestinal cholesterol absorption efficiency among inbred strains of mice.

Interindividual and interstrain variations in cholesterol absorption efficiency occur in humans and animals. We investigated physiological biliary and small intestinal factors that might determine variations in cholesterol absorption efficiency among inbred mouse strains. We found that there were significant differences in cholesterol absorption efficiency measured by plasma, fecal, and lymphatic methods: <25% in AKR/J, C3H/J, and A/J strains; 25-30% in SJL/J, DBA/2J, BALB/cJ, SWR/J, and SM/J strains; and 31-40% in C57L/J, C57BL/6J, FVB/J, and 129/SvJ strains. In (AKRxC57L)F1 mice, the cholesterol absorption efficiency (31 +/- 6%) mimicked that of the C57L parent (37 +/- 5%) and was significantly higher than in AKR mice (24 +/- 4%). Although biliary bile salt compositions and small intestinal transit times were similar, C57L mice displayed significantly greater bile salt secretion rates and pool sizes than AKR mice. In examining lymphatic cholesterol transport in the setting of a chronic biliary fistula, C57L mice displayed significantly higher cholesterol absorption rates compared with AKR mice. Because biliary and intestinal transit factors were accounted for, we conclude that genetic variations at the enterocyte level determine differences in murine cholesterol absorption efficiency, with high cholesterol absorption likely to be a dominant trait. This study provides baseline information for identifying candidate genes that regulate intestinal cholesterol absorption at the cellular level.

Animals↗
PubMed2000

[Pharmacokinetic study on absorption of stachyose].

OBJECTIVE: To study the intestinal absorption and absorption site of stachyose, one of the oligosaccharides extracted from Rehmannia, in mice and rats. METHODS: Plasma concentration of stachyose was measured by high performance liquid chromatography (HPLC) with postcolumn fluorescence derivatization after administration of stachyose to mice by oral or intravenous injection. The absorption of stachyose in different sections of digestive tract was evaluated using the intestine loop in situ technique. The kanamycin treated mice were used to study the metabolism of stachyose in intestine. RESULTS: Absorption of stachyose in intestine after oral administration was quick but low, the bioavailability being 3.82%. The absorption rate in stomach, duodenum, jejunum and ileum was 6.03%, 13.80%, 8.33% and 0.53% respectively, no absorption was tested in large intestine. The residual rate of stachyose in the intestine of normal mice and kanamycin treated mice was 8.6% and 93.4% respectively. CONCLUSION: The intestinal absorption rate of stachyose is low, the main absorption site is the upper portion of small intestine. The unabsorbed stachyose is metabolized by the intestinal microflora.

Animals↗
PubMed1998

[Kinetic effect of testosterone or estradiol on iodine absorption in castrating rat intestine].

OBJECTIVE: To observe the effect of testosterone or estradiol on iodine absorption in rat intestine. METHOD: 50 male adult Wistar rats were divided into 5 groups randomly. 50 females were divided into another 5 groups. Among them, 4 groups were bilaterally testectomized or ovariectomized, 1 group was sham-operated. 7 days after operation, the castrated rats received testosterone (male rats) or estradiol (female rats) at different dosages by intramuscular injection for three days. Then the kinetics of iodine absorption in jejunum and ileum were observed by perfusion in situ. When finished, serum were obtained for detecting TSH, T4 and testosterone or estradiol. RESULTS: In castrated male rats, the value of K12 reduced, K21 increased, K02 reduced, and SP1/2 (the half time of the slow phase) prolonged, implying that the ability of iodine absorption reduced. It reflected that testosterone could promote iodine absorption in intestine in physiological condition. In castrated female rats, the situation was different from that in male rats, the value of K12 increased, K21 reduced, K02 increased, and SP1/2 shortened in jejunum, implying that the ability of iodine absorption increased. It reflected that estradiol could inhibit iodine absorption in intestine in physiological condition. The levels of serum TSH and T4 were not changed significantly in this experiment. CONCLUSION: In physiological condition, testosterone can promote iodine absorption, while estradiol has the inhibiting effect. The results indicate that gonadol hormone maybe one factor which can influence iodine absorption in intestine. It may explain the phenomenon that the incidence of goiter is different between males and females partly.

Animals↗
PubMed2002

Water absorption enhances the uptake of mannitol and decreases Cr-EDTA/mannitol permeability ratios in cat small intestine in situ.

BACKGROUND: Recently, we hypothesized that mannitol absorption in human intestinal permeability tests is a reflection of small intestinal water absorption and is dependent mainly on the efficiency of the countercurrent multiplier in the villi. This may affect the outcome of clinical double-sugar permeability tests. We tested the hypothesis in cats, another species with an efficient countercurrent multiplier. METHODS: The lumen-to-tissue transport of [14C]mannitol and [51Cr]EDTA was studied in in situ perfused jejunum of eight anaesthetized cats using four isotonic perfusion solutions with varying sodium and glucose content. The transport of water was monitored, and the absorption rate of the probes was calculated by their disappearance from the perfusate. RESULTS: There was a significant positive correlation between water absorption and [14C]mannitol clearance from the different perfusates (r = 0.99; P < 0.01), whereas this correlation was absent for [51Cr]EDTA clearance (r = 0.05; P = 0.95). There was also a significant negative correlation between water absorption and [51Cr]EDTA/[14C]mannitol clearance ratios (r = 0.98; P < 0.02). CONCLUSIONS: The results show a prominent effect of water absorption on mannitol uptake through pores which, also during glucose transport, exclude Cr-EDTA. The difference in water absorption from the solutions used in cat small intestine is dependent on the effectiveness of the countercurrent multiplier; we conclude that the capability of this mechanism influences mannitol absorption in vivo. Qualitatively comparable results were obtained using oral test solutions with varying NaCl and glucose concentrations in human volunteers. We propose that the functioning of the countercurrent multiplier is essential for the interpretation of double-sugar tests in clinical studies.

Adult↗