Jejunal Absorption Research Articles

Meal-induced jejunal absorption requires intact neural pathways

A signal for meal-induced absorption originates from the small intestine and is transmitted to a luminally excluded segment of the proximal jejunum (Thiry-Vella [TV] fistula). Using intraluminal topical anesthesia with oxethazaine, this study assessed the role of intestinal neural pathways in basal and postprandial jejunal water and electrolyte absorption. Studies (n = 45) were performed on dogs with 25-cm proximal jejunal TV fistulae and feeding jejunostomies, using luminal perfusion with 14C-polyethylene glycol. The animals were randomized into five study groups: (1) jejunostomy oxethazaine alone, (2) jejunostomy water and jejunal meal, (3) jejunostomy oxethazaine and jejunal meal, (4) TV fistula water and jejunal meal, and (5) TV fistula oxethazaine and jejunal meal. The jejunal meal significantly increased TV fistula absorption, whereas oxethazaine significantly reduced basal absorption when administered via the TV fistula and postprandial absorption when administered via the jejunostomy (p < 0.05). TV fistula oxethazaine did not diminish the magnitude of postprandial absorption. We conclude that intact intestinal neurotransmission is necessary for maintenance of the normal basal absorptive state of the proximal jejunum and for the generation of a normal meal-stimulated proabsorptive signal from the small intestine. A nonneural mechanism appears to be of predominant importance in transmitting the proabsorptive signal from the intact gastrointestinal tract to the TV fistula.

Effect of starvation on the in vivo intestinal absorption of sugars and amino acids in young chickens (Gallus domesticus).

The effect of different patterns of starvation (acute and intermittent) on the in vivo intestinal absorption of glucose and tryptophan during the first days of Gallus domesticus chicks life was measured. Both acute and intermittent starvation increase duodenal absorption of glucose and jejunal absorption of tryptophan. Intermittent starvation tends to reduce the effect of age which normally decreases intestinal uptake of nutrients. This effect is clearer for glucose absorption than for tryptophan absorption.

Only pharmacological doses of atrial natriuretic peptide affect intestinal ion transport in non-volume expanded rats.

Pharmacological doses of atrial natriuretic peptide were infused into rats to study its effect on intestinal transport. Saline control or two concentrations of rat alpha atrial natriuretic peptide (0.06 or 1.0 nmol/min/kg) were administered intravenously (1 ml) over one hour. Jejunal net transport of water and electrolytes was measured with a plasma-like luminal electrolyte solution using a 'closed loop' technique. Distal colonic potential difference and arterial blood pressure were monitored continuously. Blood samples for analysis of plasma atrial natriuretic peptide concentrations were taken at the end of the experiments. Plasma concentrations were increased (mean (SD) (2.1 (0.5) and 24.0 (1.1) nmol/l respectively) compared with the controls (0.023 (0.016) nmol/l). Blood pressure dropped by 30% (p less than 0.05) in both groups of rats receiving atrial natriuretic peptide but remained unchanged when control saline was infused. Jejunal net absorption was reduced (p less than 0.01) only in animals receiving the higher concentration of peptide (H2O from 173 (33) to 64 (69) microliters.h-1.cm-2, Na from 25.7 (5.3) to 10.9 (8.9) mumol.h-1.cm-2). Distal colonic potential difference was not affected by atrial natriuretic peptide. In conclusion massive doses of atrial natriuretic peptide are required to produce any change in intestinal salt and water transport in normal, non-volume expanded rats; these effects could be a non-specific or 'toxic' response.

Functional role of renal afferents.

Functional role of renal afferents.

The effect of E. coli STa enterotoxin on the absorption of weakly dissociable anti‐malarial drugs from rat intestine in vivo

1. The effect of E. coli heat stable (STa) enterotoxin on the absorption of radiolabelled anti-malarial weak bases and their appearance in peripheral blood was assessed in vivo by a recirculation procedure in rat intestinal loops. 2. Enterotoxin increased the jejunal disappearance of quinine (P less than 0.05), trimethoprim (P less than 0.05), proguanil (P less than 0.05) and chloroquine (P less than 0.001) and left pyrimethamine disappearance unaltered. Peripheral blood levels of trimethoprim (P less than 0.02) and proguanil (P less than 0.05) were higher after STa exposure. 3. In the ileum, enterotoxin increased the luminal disappearance (P less than 0.05) and peripheral blood appearance (P less than 0.001) of chloroquine. The luminal disappearance rate of trimethoprim was reduced (P less than 0.05) and that of pyrimethamine unchanged. 4. The increased jejunal absorption of the anti-malarial drugs occurred despite STa causing a reduction in the amount of net fluid absorption. It seems likely that the enhanced absorption with STa exposure is related to the effect of STa on the microclimate pH. An elevation in the microclimate pH would increase the amount of undissociated weak base available for non-ionic diffusion. 5. The favourable elevation of microclimate pH by STa seemed to be outweighted by the reduced fluid absorption in the ileum. Only chloroquine still showed enhanced absorption in the ileum and this may have been because unlike the other antimalarial drugs, chloroquine has two dissociable groups likely to be affected by the mucosal surface pH changes.

The Migrating Motor Complex and the Enterohepatic Circulation of Bile Acids: A Scintigraphic Study Using 75Se‐HCAT

The relationship between the migrating motor complex (MMC) and the enterohepatic circulation was studied in 16 healthy young male volunteers using a combined technique of continuous pressure recording from the gastroduodenal region and scintigraphy with 75Se‐homo‐cholic‐acid‐taurine (75Se‐HCAT). In nine subjects (group 1) the radioactive marker was instilled in the duodenum immediately before a phase III complex of the MMC, and in seven subjects (group 2) in early phase II. In group 1, the gallbladder was visualized by scintigraphy at a median time of 45 (27–90) minutes after instillation of 75Se‐HCAT. Median time for peak radioactivity in distal small intestine and in peripheral blood was 63 (36–144) minutes and 90 (63–135) minutes, respectively. The corresponding figures in group 2 were 108 (81–117), 117 (81–162), and 153 (117–180) minutes. The differences between the median values in the two groups were significant (p &lt; 0.05). The present results demonstrate the importance of phase III in the transport of bile through the small intestine. In addition, they support the contention of jejunal absorption of cholic‐acid‐taurine.

Absorption of hexose and pentose sugars in vivo in perfused intestinal segments in the fowl

1. 1. Rates of absorption of two hexose ( d-glucose and d-galactose) and two pentose ( d-xylose and d-arabinose) sugars were measured by in vivo perfusion, in jejunum, ileum and (distal) caecum, in immature hens conditioned to either a standard (ST) or “high fibre” (ST + 20% grass) diet. 2. 2. Each bird was tested in one intestinal segment with all four (U- 14C-labelled, 10 mM) sugars, with either the hexoses preceding the pentoses or vice versa. 3. 3. With all treatments, absorption rates of the hexoses were alike, as were those of the pentoses. Hexose absorption was twice as fast as pentose absorption in jejunum and ileum with both dietary pretreatments, whereas in caecum hexose and pentose rates were similarly high, except when pentose (and its associated fluid transfer) was apparently inhibited by prior hexose absorption with the ST diet. 4. 4. With the ST diet, hexose absorption (per unit length and dry weight) was faster in caecum than in jejunum and ileum, and pentose absorption was also fastest in caecum when all pentose data from testing after hexose were excluded. 5. 5. With the ST/grass diet, hexose absorption was faster in jejunum than in ileum and caecum when expressed per unit length, and pentose absorption was fastest in caecum on a dry weight basis. 6. 6. Hexose absorption was faster in jejunum and slower in caecum with the ST/grass pretreatment than with ST. However, the dietary comparison was not conclusive because it involved birds from (two) different hatches (of similar age and weight) tested at different times.

Jejunal absorption, pharmacological activity, and pharmacokinetic evaluation of indomethacin-loaded poly(d,l-lactide) and poly(isobutyl-cyanoacrylate) nanocapsules in rats.

The jejunal absorption of indomethacin nanocapsules was studied using an in vivo infusion technique. Jejunal absorption of indomethacin from the nanocapsules was slightly delayed as compared to a commercial indomethacin solution. The plasma and jejunal mucosa indomethacin concentrations were similar in both cases. However, the nanocapsules protected the rat jejunum from the ulcerating effect of indomethacin, probably by avoiding direct contact of the free drug with the surface of the mucosa. The pharmacokinetic profile of indomethacin nanocapsule formulations was compared to a solution of free drug following oral administration of 5 mg/kg in rats; no difference in the mean concentration-time profiles of the drug was observed. Blood levels of thromboxane showed a sustained biological activity, over a period of 24 hr, of indomethacin-loaded nanocapsules, relative to the drug in solution, following oral administration.

Effects of portal infusion of hypertonic solution on jejunal electrolyte transport in anesthetized dogs

Jejunal electrolyte absorption was measured in the jejunal loops of anesthetized dogs during infusions of hypertonic solutions via the portal vein. The net Na absorption was not influenced by the 9% NaCl infusion into the inferior vena cava, although it was significantly attenuated by the portal 9% NaCl infusion. This effect may not be due to the osmotic stimulus, since the portal 50% glucose or 6.5% LiCl infusion had no significant influence on the net Na absorption. To determine the mechanism of the decrease in the net Na absorption during the portal hypertonic NaCl infusion, the net Na absorption was measured after the section of anterior and posterior hepatic nerves (SAPH) or intravenous atropine injection. Both SAPH and the intravenous atropine injection completely blocked the effect of the portal 9% NaCl infusion on the net Na absorption. These results indicate that 1) net Na absorption in dog jejunum is depressed by the hypertonic NaCl infusion via the portal vein; 2) the effect is NaCl specific and may not be due to the osmotic stimulus; and 3) the afferent limbs of this effect are the anterior and posterior hepatic nerves, and the efferent limb of this effect is the vagus nerve. Thus the hepatojejunal reflex may play an important role in the regulation of body fluid homeostasis.

Modulation of fluid absorption and the secretory response of rat jejunum to cholera toxin by dietary fat.

To study the effects of dietary fat on jejunal water and ion absorption and on cholera toxin-induced secretion, 3 week old Sprague Dawley rats were fed isocaloric diets. Forty per cent of the total calories were given as fat, as butter (high saturated fat), olive oil (high monounsaturated fat), or corn oil (high polyunsaturated fat), with one group on low fat (10% of calories) standard laboratory diet as controls. During in vivo jejunal perfusion studies we found that (i) a polyunsaturated fat (corn oil) supplemented diet improves jejunal absorption of water and electrolytes and these changes are independent of the observed concentrations of luminal prostaglandins; (ii) high dietary fat appreciably reduced the secretory response to cholera toxin, probably without fundamentally changing the mechanism by which cholera toxin induces secretion. We conclude that dietary fat composition altered the permeability and transport characteristics of the small intestine. This observation might have relevance to some human diarrhoeal disorders.

Arachidonic acid absorption in human jejunum in organ culture: effects of ethanol

Abstract. Human jejunal tissue obtained by peroral biopsy was cultured in control medium and in medium containing 100 mmol 1‐1 ethanol. Subsequently, the incorporation and metabolism of [3H]‐arachidonic and [14C]‐linoleic acid were evaluated. Of the two fatty acids a significantly higher amount of [3]‐arachidonic acid was incorporated into phospholipids and more [14.C]‐linoleic acid was incorporated into triacylglycer‐ols. This preferential distribution of the labelled fatty acids was not affected by ethanol, but when ethanol was present in the tissue culture medium, there was a significant decrease in the incorporation of both fatty acids into tissue phospholipids. The study thus shows that ethanol in moderate concentrations can affect human jejunal absorption and metabolism of poly‐enoic fatty acids, contributing to a decrease in the amount of eicosanoid precursors available in jejunal tissue.

Arachidonic acid absorption in human jejunum in organ culture: effects of ethanol

Human jejunal tissue obtained by peroral biopsy was cultured in control medium and in medium containing 100 mmol l-1 ethanol. Subsequently, the incorporation and metabolism of [3H]-arachidonic and [14C]-linoleic acid were evaluated. Of the two fatty acids a significantly higher amount of [3H]-arachidonic acid was incorporated into phospholipids and more [14C]-linoleic acid was incorporated into triacylglycerols. This preferential distribution of the labelled fatty acids was not affected by ethanol, but when ethanol was present in the tissue culture medium, there was a significant decrease in the incorporation of both fatty acids into tissue phospholipids. The study thus shows that ethanol in moderate concentrations can affect human jejunal absorption and metabolism of polyenoic fatty acids, contributing to a decrease in the amount of eicosanoid precursors available in jejunal tissue.

Meal-stimulated absorption of water and electrolytes in canine jejunum

After a meal, the absorption of water and electrolytes from the jejunal lumen increases. This meal-induced jejunal absorption occurs in jejunal segments out of normal gastrointestinal continuity. The experimental model used 25-cm proximal jejunal Thiry-Vella loops in awake dogs (n = 72 observations) to evaluate the mechanisms involved in meal-induced jejunal absorption, seeking to define the source or sources of the proabsorptive signal. Specifically, we evaluated the jejunal absorptive response to a standard meal, a standard meal plus cholinergic blockage using atropine, a sham-fed meal, a gavage-fed meal, and gastric distension with balloon and gavage water. Both the standard meal and the gavage-fed meal induced a prompt, sustained, and significant (P less than 0.0001) increase in the absorption of H2O, Na+, and Cl-. Atropine significantly reduced the magnitude of the postmeal absorptive response (P less than 0.05) compared with the standard meal alone. The sham-fed meal, gastric balloon distension, and gavage water did not alter jejunal absorption. Vagal nerve integrity after cervical esophageal manipulation was verified by gastric acid output and gastrin response to stimuli. These data support a role for cholinergic modulation of meal-stimulated jejunal absorption via a cephalic-phase-independent and gastric-distension-independent mechanism.

In vivo transport kinetics and distribution of taurocholate by rat ileum and jejunum

The transport kinetics and distribution of taurocholate (TC) from the ileum and jejunum were evaluated in anesthetized Sprague-Dawley rats. Uptake and transport kinetics were determined after simultaneous administration of equimolar solutions of [3H]taurocholic acid ([3H]TC) in the ileum and [24-14C]taurocholic acid ([14C]TC) in the jejunum of anesthetized rats. At TC concentrations between 0.3 and 15 mM, total ileal absorption exceeded jejunal absorption 15- to 25-fold. The apparent Km and Vmax for ileal absorption of TC were 5.6 mM and 65.5 nmol.min-1.cm-1, respectively. Tissue distribution studies following uptake from the ileum and jejunum were done with 75Se-labeled homocholic acid taurine (75Se-HCAT). In the ileum, 82% of the 75Se-HCAT removed from the lumen was found in the bile, 10.6% was found in the ileal wall, and 7.3% was found in the liver. In the jejunum, 24.1% was found in bile, 0.6% was found in the liver, and 75.3% remained in the jejunal wall. These data show that the ileum is much more efficient and better equipped than the jejunum to take up and transport TC at concentrations up to 15 mM.

Development of the Neonatal Rat Small Intestinal Barrier to Nonspecific Macromolecular Absorption: Effect of Early Weaning to Artificial Diets

We studied the effect of early weaning from maternal breast milk to artificial diets on rat jejunal absorption of an exogenous 40-kD glycoprotein, horseradish peroxidase (HRP). Rat pups, fed maternal milk (MM) from birth, received one of three diets for the last 4 d before weaning (d 17-21): MM, protein hydrolysate formula (PH), or soy formula (S). Some rats were pretreated on d 14 with intraperitoneal hydrocortisone (5 mg/rat). In MM-fed rat pups, jejunal HRP absorption was markedly higher on d 17 than on d 21. [Geometric means (95% confidence interval) were: d 17, 626.4 (461.3, 850.6) versus d 21, 90.6 (48.2, 170.5) IU HRP/mL x cm x min, p less than 0.01.] By contrast, 21-d-old PH- and S-fed pups maintained elevated absorption of the tracer [PH, 292.3 (177.5, 480.6), p less than 0.05 versus MM pups, S, 340.8 (164.4, 704.8), p less than 0.01 versus MM pups]. Wt-matched control studies indicate that the difference in HRP absorption was not due to the smaller body wt of formula-fed pups. The increased absorption in formula-fed animals was suppressed by hydrocortisone. In S-fed pups, the increased macromolecular absorption appeared, in part, to be the result of diffusion across altered villus absorptive cells. In PH-fed pups, there was no evidence of damage and HRP absorption appeared to occur by vesicle-mediated transport. Delay in the normal maturation of small intestinal "closure" appears to be associated with early weaning to artificial diets. This may lead to increased nonspecific macromolecular permeability that could result in immune-mediated sensitization and food intolerance.

Intestinal Absorption of Amiodarone in Man

The jejunal absorption rate of amiodarone and the influence of lipids on it were studied in human volunteers using the intestinal perfusion technique. A nutrient solution (Realmentyl, Sopharga Laboratories, France) with 300 mg of the drug was infused for 120 minutes at the ligament of Treitz. The segment tested was 25 cm long. Two caloric loads of the nutrient solution, 3.3 Kcal/min (solution A) and 1.3 Kcal/min (solution B), A containing total lipid and caloric load 2.5 times higher than B, were administered. Minor interindividual differences in amiodarone absorption rate were observed (20.2 to 31.7%) with solution A. Amiodarone absorption correlated with lipid absorption significantly. Since the maximal plasma concentrations of the drug and the area under the curve (AUC/24 hours) did not correlate with the amount of amiodarone absorbed, the wide fluctuations of amiodarone pharmacokinetics must mainly be due to amiodarone tissue distribution and metabolic pathway.

Effect of radiation on glucose absorption in the mouse jejunum in vivo

In an attempt to develop a clinical assay for intestinal damage, the relationship between radiation dose and glucose absorption in the jejunum has been investigated. Lightly anesthetised C3D2F 1 mice had their upper abdomen irradiated. The intestine was exteriorized and a 10-cm segment of the jejunum was isolated and included in a closed circuit perfusion loop. An isotonic solution containing 2 mg/ml D-glucose was perfused in 2 h and the rate of glucose absorption calculated. The absorption decreased as a function of dose and time after irradiation with the most prominent reduction after 4–5 days, returning to normal within a week after irradiation. A dose-response relationship was found after single doses between 5 and 17.5 Gy. Split-dose recovery of approximately 7.5 Gy was found within 2–4 h. This absorption insufficiency was only found to be present acutely, and no late abnormalities were seen for times greater than 12 months after irradiation. The results correlated with other functional endpoints such as absorptive surface. This assay seems suitable to demonstrate (acute) functional intestinal radiation damage and has obvious clinical applicability.

Absorption of triglycerides in the absence of lipase

Medium chain triglycerides are considered to be readily absorbed intact in the absence of pancreatic lipase, unlike long chain triglycerides. Commercial medium chain triglyceride oils comprise various medium chain fatty acids from 6 to 12 carbons in length resulting in triglyceride molecules of different sizes and molecular weights. The effect of molecular weight and hence fatty acid chain length on the efficiency of intact medium chain triglyceride absorption is unknown. Therefore, this study measured, using a single-pass marker perfusion technique, intestinal jejunum absorption of five medium chain and one long chain triglycerides in anesthetized Sprague-Dawley rats. The molecular weights of the five medium chain triglycerides were 470.7, 498.8, 526.8, 554.9, 639.0, and the long chain triglyceride, 885.4. Residual luminal pancreatic lipase was removed prior to lipid perfusion. This study demonstrated that medium chain triglycerides were absorbed in the absence of lipase whereas long chain triglyceride was not. There was no significant variation in the absorption of the five different medium chain triglycerides perfused. The molecular weight of the medium chain triglyceride did not affect its intact absorption by the small intestine.

Jejunal and Heal Glucose-Stimulated Water and Sodium Absorption in Tropical Enteropathy: Implications for Oral Rehydration Therapy

Intestinal glucose and water absorption in response to glucose has been studied in tropical enteropathy with a view to determine the optimum glucose concentration in oral rehydration solutions for use in the tropics. Maximum jejunal water and sodium absorption occurred from an 80-mM glucose-sodium chloride solution (-285.7 +/- 46.0 ml/30 cm/h and -31.8 +/- 3.8 mM/30 cm/h, respectively) during in vivo steady-state jejunal perfusion. At perfusate glucose concentrations greater than 250 mM, however, jejunal water and sodium secretion occurred. In the ileum, maximum glucose-stimulated water absorption (-91.1 +/- 27.1 ml/30 cm/h) was significantly less than in the jejunum. Glucose absorption demonstrated saturation kinetics in both the jejunum and ileum. The half-saturation concentration was higher in the jejunum (167 mM) compared to the ileum (28 mM). This study suggests that the optimal glucose concentration for oral rehydration solutions used in the tropics should be 80 mM, as lower and higher concentrations result in diminished jejunal water absorption.

Effect of lactose or its component sugars on jejunal calcium absorption in adult man

The effect of lactose vs glucose plus galactose on jejunal calcium absorption was studied in 10 subjects using a triple-lumen perfusion technique. In each, 30 cm of jejunum was perfused with two test solutions. The comparisons made were lactose (Lac) vs mannitol (Man), Lac vs glucose and galactose (GG), and Man vs GG. Compared with Man, Lac, and GG caused a significant increase in net water and sodium absorption and luminal calcium concentration. In subjects receiving both Lac and GG, water and sodium absorption were greater with GG. The only statistically significant increase in net calcium absorption occurred with Man vs GG in which water absorption increased from 16 to 350 mL.h-1.30 cm-1. However, by use of data from all test solutions, water and sodium absorption were found to be significantly correlated with calcium absorption (p less than 0.05). These results suggest that lactose or its component sugars enhance jejunal calcium absorption in proportion to their effect on fluid absorption.