Rat Jejunum Research Articles

Dietary supplementation with Agaricus blazei murill extract prevents diet‐induced obesity and insulin resistance in rats

Dietary supplement may potentially help to fight obesity and other metabolic disorders such as insulin-resistance and low-grade inflammation. The present study aimed to test whether supplementation with Agaricus blazei murill (ABM) extract could have an effect on diet-induced obesity in rats. Wistar rats were fed with control diet (CD) or high-fat diet (HF) and either with or without supplemented ABM for 20 weeks. HF diet-induced body weight gain and increased fat mass compared to CD. In addition HF-fed rats developed hyperleptinemia and insulinemia as well as insulin resistance and glucose intolerance. In HF-fed rats, visceral adipose tissue also expressed biomarkers of inflammation. ABM supplementation in HF rats had a protective effect against body weight gain and all study related disorders. This was not due to decreased food intake which remained significantly higher in HF rats whether supplemented with ABM or not compared to control. There was also no change in gut microbiota composition in HF supplemented with ABM. Interestingly, ABM supplementation induced an increase in both energy expenditure and locomotor activity which could partially explain its protective effect against diet-induced obesity. In addition a decrease in pancreatic lipase activity is also observed in jejunum of ABM-treated rats suggesting a decrease in lipid absorption. Taken together these data highlight a role for ABM to prevent body weight gain and related disorders in peripheral targets independently of effect in food intake in central nervous system.

Anti-hyperglycemic Effect of the Aqueous Extract of Banana Infructescence Stalks in Streptozotocin-induced Diabetic Rats

Water extract of banana (Musa sapientum) infructescence stalks has been used in folk medicine in the treatment of diabetes mellitus. This work aims at verifying the claimed effect and elucidating its possible mode of action. The extract was given in replacement of drinking water to diabetic rats, and its mechanism of action was studied by investigating its involvement in glucose transport in Caco-2 monolayers, and in rat jejuna using an in situ perfusion technique. Its effect on the Na(+)/K(+) ATPase was studied by measuring the amount of inorganic phosphate liberated. The extract reduced significantly blood glucose levels in diabetic rats and glucose transport across rat jejuna and Caco-2 monolayers, and induced a 50% decrease in their Na(+)/K(+) ATPase activity. The extract did not induce any further decrease in jejunal glucose uptake in the simultaneous presence of phloridzin and phloretin, respective inhibitors of SGLT1 and GLUT2 transporters nor did it induce a change in the protein expression of SGLT1 and GLUT2. It was concluded that the extract acts by reducing the Na(+)/K(+) ATPase activity of enterocytes and consequently the sodium gradient required for sugar transport by SGLT1, which leads to down-regulation of GLUT2 and contributes to the observed anti-hyperglycemic effect.

Comparison of the Permeability of Metoprolol and Labetalol in Rat, Mouse, and Caco-2 Cells: Use as a Reference Standard for BCS Classification

The purpose of this study was to investigate labetalol as a potential high permeability reference standard for the application of Biopharmaceutics Classification Systems (BCS). Permeabilities of labetalol and metoprolol were investigated in animal intestinal perfusion models and Caco-2 cell monolayers. After isolating specific intestinal segments, in situ single-pass intestinal perfusions (SPIP) were performed in rats and mice. The effective permeabilities (Peff) of labetalol and metoprolol, an FDA standard for the low/high Peff class boundary, were investigated in two different segments of rat intestine (proximal jejunum and distal ileum) and in the proximal jejunum of mouse. No significant difference was found between Peff of metoprolol and labetalol in the jejunum and ileum of rat (0.33 ± 0.11 × 10(-4) vs 0.38 ± 0.06 × 10(-4) and 0.57 ± 0.17 × 10(-4) vs 0.64 ± 0.30 × 10(-4) cm/s, respectively) and in the jejunum of mouse (0.55 ± 0.05 × 10(-4) vs 0.59 ± 0.13 × 10(-4) cm/s). However, Peff of metoprolol and labetalol were 1.7 and 1.6 times higher in the jejunum of mouse, compared to the jejunum of rat, respectively. Metoprolol and labetalol showed segmental-dependent permeability through the rat intestine, with increased Peff in the distal ileum in comparison to the proximal jejunum. Most significantly, Peff of labetalol was found to be concentration-dependent. Decreasing concentrations of labetalol in the perfusate resulted in decreased Peff compared to Peff of metoprolol. The intestinal epithelial permeability of labetalol was lower than that of metoprolol in Caco-2 cells at both apical pH 6.5 and 7.5 (5.96 ± 1.96 × 10(-6) vs 9.44 ± 3.44 × 10(-6) and 15.9 ± 2.2 × 10(-6) vs 23.2 ± 7.1 × 10(-6) cm/s, respectively). Labetalol exhibited higher permeability in basolateral to apical (BL-AP) compared to AP-BL direction in Caco-2 cells at 0.1 times the highest dose strength (HDS) (46.7 ± 6.5 × 10(-6) vs 14.2 ± 1.5 × 10(-6) cm/s). The P-gp inhibitor, verapamil, significantly increased AP-BL and decreased BL-AP direction transport of labetalol. Overall, labetalol showed high Peff in rat and mouse intestinal perfusion models similar to metoprolol at a concentration based on HDS. However, the concentration-dependent permeability of labetalol in mice due to P-gp and the inhibition study with verapamil in Caco-2 cells indicated that labetalol is not an ideal reference standard for BCS classification.

Characterization of Efflux Transporters Involved in Distribution and Disposition of Apixaban

The studies reported here were conducted to investigate the transport characteristics of apixaban (1-(4-methoxyphenyl)-7-oxo-6-(4-(2-oxopiperidin-1-yl)phenyl)-4,5,6,7-tetrahydro-1H-pyrazolo[3,4-c]pyridine-3-carboxamide) and to understand the impact of transporters on apixaban distribution and disposition. In human permeability glycoprotein (P-gp)- and breast cancer resistance protein (BCRP)-cDNA-transfected cell monolayers as well as Caco-2 cell monolayers, the apparent efflux ratio of basolateral-to-apical (PcB-A) versus apical-to-basolateral permeability (PcA-B) of apixaban was >10. The P-gp- and BCRP-facilitated transport of apixaban was concentration- and time-dependent and did not show saturation over a wide range of concentrations (1-100 μM). The efflux transport of apixaban was also demonstrated by the lower mucosal-to-serosal permeability than that of the serosal-to-mucosal direction in isolated rat jejunum segments. Apixaban did not inhibit digoxin transport in Caco-2 cells. Ketoconazole decreased the P-gp-mediated apixaban efflux in Caco-2 and the P-gp-cDNA-transfected cell monolayers, but did not affect the apixaban efflux to a meaningful extent in the BCRP-cDNA-transfected cell monolayers. Coincubation of a P-gp inhibitor (ketoconazole or cyclosporin A) and a BCRP inhibitor (Ko134) provided more complete inhibition of apixaban efflux in Caco-2 cells than separate inhibition by individual inhibitors. Naproxen inhibited apixaban efflux in Caco-2 cells but showed only a minimal effect on apixaban transport in the BCRP-transfected cells. Naproxen was the first nonsteroidal antiinflammatory drug that was demonstrated as a weak P-gp inhibitor. These results demonstrate that apixaban is a substrate for efflux transporters P-gp and BCRP, which can help explain its low brain penetration, and low fetal exposures and high milk excretion in rats.

P067 Human and rodent ex vivo model for intestinal fibrosis in inflammatory bowel disease (IBD)

Background: One of the major complications in IBD is intestinal fibrosis (IF). It is the result of the chronic inflammation of intestinal tissue. IF causes narrowing of the intestinal lumen and potential stricture formation. For the study of the cellular and molecular mechanism of IF in IBD adequate animal models are lacking. Our aim is to develop an ex vivo model for IF by using human and rodent precision-cut intestinal slice (PCIS). In PCIS all cell types are present in their original tissue-matrix environment and can be used as a model to study the early onset of IF. Methods: Rat, mouse and human jejunum were excised and prepared as a segment embedded in agarose. PCIS (estimated 300-400 mm) was prepared and incubated up to 24 hr (rat) or 48 hr (human and mouse). ATP content of the PCIS was used to assess the general viability. Moreover, morphology (rat and human) was evaluated. The gene expression of different fibrosis markers including Pro-Collagen 1 A1 (COL1A1), Heat Shock Protein 47 (HSP47), alpha-Smooth Muscle Actin (SMA), connective tissue growth factor (CTGF), Synaptophysin (SYN) and Fibronectin (FIB) were determined. Results: Mouse PCIS were viable up to 48 hr. However, for rat and human PCIS ATP content was decreased to 25% (24hr) and 70% (48 hr), respectively. ATP content of rat and human PCIS correlated well with morphology of the PCIS. In rat PCIS, after 24 hr, HSP47 (3.2 fold) and FIB (2.1 fold) gene expressions were significantly increased. In the presence of 5 ng/mL TGF-β, COL1A1 (1.8 fold), SMA (1.5 fold) and CTGF (2.1 fold) were significantly up-regulated compared to 24 hr control. Meanwhile HSP47 gene expression was slightly decreased (0.8 fold). Similarly, in mouse PCIS, gene expression of HSP47 (3.9 fold) and FIB (4.3 fold) was significantly increased after 48 hr. When incubated with 5 ng/mL TGF-β, COl1A1 and FIB were significantly up-regulated (2.0 fold) compared to 48 hr control, HSP47 and CTGF gene expression were slightly, but significantly increased (1.2 fold). In human PCIS, after 48 hr, HSP47 (3.5-fold) and SYN (2.5 fold) were significantly up-regulated. However, incubation of human PCIS with 5 ng/ml of TGF-β, none of the investigated fibrosis genes was affected. Conclusions: In rat, mouse and human PCIS an increase in gene expression of early-onset of fibrosis makers was found. In addition, TGF-β was able to induce fibrosis markers in rat and mouse, but not in human PCIS. Rodent and human PCIS are promising ex vivo models to study the early onset of intestinal fibrosis.

Antidiabetic Properties and Mechanism of Action of Orthosiphon stamineus Benth Bioactive Sub-fraction in Streptozotocin-induced Diabetic Rats

Orthosiphon stamineus is a popular folk medicine widely used to treat many diseases including diabetes. Previous studies have shown that the sub-fraction of chloroform extract was able to inhibit the rise of blood glucose levels in a glucose tolerance test. This study was carried out to evaluate the chronic effect and possible mechanism of action of the bioactive chloroform sub-fraction of O. stamineus using streptozotocin-induced diabetic rats and in vitro methods. Administration of the chloroform extract sub-fraction 2 (Cƒ2-b) at a dose of 1 g/kg twice daily on diabetic rats for 14 days showed a significant lowering (p < 0.05) of the final blood glucose level compared to the pretreatment level. However, there were no significant differences in the plasma insulin levels post-treatment compared to the pretreatment levels for all doses of Cƒ2-b. Conversely, Cƒ2-b at a concentration of 2 mg/mL significantly increased (p < 0.001) the glucose uptake by the rat diaphragm muscle. The increase in glucose uptake was also shown when the muscle was incubated in a solution containing 1 IU/mL of insulin or 1 mg/mL of metformin. Furthermore, the effect of this sub-fraction on glucose absorption in the everted rat jejunum showed that Cƒ2-b at concentrations of 0.5 mg/mL, 1 mg/mL and, 2 mg/mL significantly reduced the glucose absorption of the jejunum (p < 0.05–0.001). Similarly, the absorption of glucose was also inhibited by 1 mg/mL and 2 mg/mL of metformin (p < 0.001). These results suggest that the effect of Cƒ2-b may be due to extra-pancreatic mechanisms. There was no evidence that the plant extract stimulated the release of insulin in order to lower the blood glucose level.

Corticosterone mediates stress‐related increased intestinal permeability in a region‐specific manner

Chronic psychological stress (CPS) is associated with increased intestinal epithelial permeability and visceral hyperalgesia. It is unknown whether corticosterone (CORT) plays a role in mediating alterations of epithelial permeability in response to CPS. Male rats were subjected to 1-h water avoidance (WA) stress or subcutaneous CORT injection daily for 10 consecutive days in the presence or absence of corticoid receptor antagonist RU-486. The visceromotor response (VMR) to colorectal distension (CRD) was measured. The in situ single-pass intestinal perfusion was used to measure intestinal permeability in jejunum and colon simultaneously. We observed significant decreases in the levels of glucocorticoid receptor (GR) and tight junction proteins in the colon, but not the jejunum in stressed rats. These changes were largely reproduced by serial CORT injections in control rats and were significantly reversed by RU-486. Stressed and CORT-injected rats demonstrated a threefold increase in permeability for PEG-400 (MW) in colon, but not jejunum and significant increase in VMR to CRD, which was significantly reversed by RU-486. In addition, no differences in permeability to PEG-4000 and PEG-35 000 were detected between control and WA groups. Our findings indicate that CPS was associated with region-specific decrease in epithelial tight junction protein levels in the colon, increased colon epithelial permeability to low molecular weight macromolecules which were largely reproduced by CORT treatment in control rats and prevented by RU-486. These observations implicate a novel, region-specific role for CORT as a mediator of CPS-induced increased permeability to macromolecules across the colon epithelium.

Inhibiting Roles of Berberine in Gut Movement of Rodents are Related to Activation of the Endogenous Opioid System

Although Berberine (BER) is popular in treating gastrointestinal (GI) disorders, its mechanisms are not clear yet. In order to investigate the effects and possible mechanism of BER on GI motility in rodents, we first explored GI motility by recording the myoelectrical activity of jejunum and colon in rats, and upper GI transit with a charcoal marker in mice. Then, the plasma levels of gastrin, motilin, somatostatin and glucagon-like-peptide-1 (Glp-1) were measured by ELISA or radioimmunoassay (RIA). Furthermore, endogenous opioid-peptides (β-endorphin, dynorphin-A, met-enkephalin) were detected by RIA after treatment with BER. Our results showed that BER concentration-dependently inhibited myoelectrical activity and GI transit, which can be antagonized by opioid-receptor antagonists to different extents. The elevated somatostatin and Glp-1, and decreased gastrin and motilin in plasma, which were caused by BER application, also could be antagonized by the opioid-receptor antagonists. Additionally, plasma level of β-endorphin, but not dynorphin-A and met-enkephalin, was increased by applying BER. Taken together, these studies show that BER plays inhibiting roles on GI motility and up-regulating roles on somatostatin, Glp-1 and down-regulating roles on gastrin, motilin. The pharmacological mechanisms of BER on GI motility and plasma levels of GI hormones were discovered to be closely related to endogenous opioid system.

Lamivudine permeability study: A comparison between PAMPA, ex vivo and in situ Single-Pass Intestinal Perfusion (SPIP) in rat jejunum

In order to reach the bloodstream and thus the target receptor, an orally-administered drug must first cross the intestinal barrier, which can occur via a paracellular, passive transcellular, or carrier-mediated uptake and/or efflux process (active or concentration gradient-driven). Our work aimed to explore the transport mechanism of the antiretroviral lamivudine (deoxycytidine nucleoside analogue), using a three-part strategy: in vitro, an ex vivo and an in situ method, represented by PAMPA, rat jejunum patches and rat Single Pass Intestinal Perfusion (SPIP), respectively. The determined permeability coefficients were compared with those from a published Caco-2 and MDCK study. Computational prediction of human jejunal permeability was explored, using various non-human permeability coefficients as descriptors. The ex vivo technique was performed in Franz-type diffusion cells, mounted with male Wistar rat jejunum segment patches. PAMPA was performed with an acceptor solution simulating the binding of serum proteins, an artificial membrane impregnated with egg lecithin/cholesterol and a gradient of pH between donor and acceptor solutions. The SPIP was conducted by proximal jejunum cannulation and drug perfusion in a constant flow rate of 0.2mL/min. The outcomes of our studies showed the following predicted pattern for lamivudine effective jejunal permeability: PeffexvivoA>B>PeffSPIP>PeffexvivoB>A>PeffCaco-2≈PeffMDCK≈PeffPAMPA, strongly suggesting that this compound has carrier-mediated uptake as its dominant transport mechanism. Notwithstanding, Caco-2 cells may indicate an under-expression of uptake transporters and possibly an over-expression efflux transporters, compared to that found in the rat jejunum.

Ultrastructural Demonstration of the Absorption and Transportation of Minute Chylomicrons by Subepithelial Blood Capillaries in Rat Jejunal Villi

ABSTRACTChylomicrons from villous columnar epithelial cells are generally known to be transported only by central lymph vessels (CLV), whereas antigenic particulates derived from the intestinal lumen can also be transported by subepithelial blood capillaries (sBCs) in rat intestinal villi. The possibility of chylomicron absorption by sBCs was histoplanimetrically studied in the rat jejunum under a transmission electron microscope. The chylomicrons more abundantly presented in villous venules than in arterioles. The most frequent size (MFS) of chylomicrons was 75 to 90 nm in diameter in the areas near sBCs, while it was 45 to 60 nm in the epithelial intercellular spaces just above sBCs or the intermediate areas between sBCs. The MFS of chylomicrons was 45 to 60 nm in the intermediate areas between sBCs and in the epithelial intercellular spaces just above these areas. The MFS of chylomicrons in CLV was intermediate between that in the area adjacent to sBCs and that in the intermediate areas between sBCs. Chylomicrons were found in small vesicles in the endothelial cytoplasms of sBCs. No chylomicrons larger than 600 nm were observed in the lamina propria. These findings suggest that some of the chylomicrons smaller than 75 nm, which are probable intestinal very low-density lipoproteins (VLDL), are directly transported to the liver by hepatic portal blood in addition to CLV and that epithelial fat droplets larger than 600 nm are not discharged into lamina propria in rat jejunum under physiological conditions.

Baicalein 6-&lt;i&gt;O&lt;/i&gt;-β-d-Glucopyranuronoside Is a Main Metabolite in the Plasma after Oral Administration of Baicalin, a Flavone Glucuronide of Scutellariae Radix, to Rats

Baicalin (BG) and its aglycone, baicalein (B) are strong antioxidants that exert various pharmacological actions and show unique metabolic fates in the rat. The aim of the present study was to identify major metabolite(s) besides BG in rat plasma after oral administration of BG or B. The main metabolite was detected by HPLC equipped with an electrochemical detector at a potential of +500 mV and identified as baicalein 6-O-β-D-glucopyranuronoside (B6G) by HPLC/MS/MS. When BG at a dose of 20 mg/kg was administered orally to Wistar rats, the level of B6G in plasma was higher than that of BG. Cmax and the area under the concentration-curve from 0 to 24 h (AUC0-24 h) values of the plasma B6G were 1.66 ± 0.34 µM and 19.8 3.9 ± µM · h, respectively, whereas those of BG were 0.853 ± 0.065 µM and 10.0 ± 3.1 µM · h, respectively. When B was administered, similar results were also obtained. B6G-producing activities from B were found in microsomes of both rat jejunum and liver, in spite of the low activity. Rat everted jejunal sacs formed B6G after application of B, but only in a small amount that was excreted into the mucosal side, and not the serosal side, indicating little contribution to the appearance of B6G in plasma. On the other hand, when B was injected into the rat portal vein, B6G was detected at a higher level than BG in the systemic circulation, demonstrating the hepatic contribution to the appearance of plasma B6G.

Tibetan herbal formula Padma Digestin modulates gastrointestinal motility in vitro

To examine the effects of Padma Digestin on the smooth muscle motility of different gastrointestinal segments in vitro. The effects of the ethanolic extract of Padma Digestin (at 8.16 mg/mL or 81.6 mg/mL) on the contractility and susceptibility to acetylcholine (ACh) of muscle strips from the cardia, antrum, pylorus, duodenum, jejunum, ileum and colon of male Wistar rats were analyzed. Compared with the control treatment, the Padma Digestin extract had a procontractile effect on the antral smooth muscle strips. Padma Digestin decreased ACh sensitivity in cardia muscle strips and increased it in those from the antrum and pylorus. In the intestinal segments, spontaneous contractility was inhibited in both the duodenal and jejunal strips, whereas reactivity to ACh was inhibited in the jejunal strips only. In the colonic samples, Padma Digestin inhibited spontaneous and ACh-stimulated contractility at a low dose but seems to have increasing effects at a high dose. Padma Digestin extract has region-specific effects on the contractility and excitability of gastrointestinal smooth muscle. Our results support the traditional use of Padma Digestin for maldigestion and functional gastrointestinal disorders.

Role of Drug Efflux and Uptake Transporters in Atazanavir Intestinal Permeability and Drug-Drug Interactions

To investigate the role of membrane-associated drug transporters in regulating the intestinal absorption of the HIV-1 protease inhibitor, atazanavir, and assess the potential contribution of these transporters in clinical interactions of atazanavir with other protease inhibitors and tenofovir disoproxil fumarate (TDF). Intestinal permeability of atazanavir was investigated in vitro, using the Caco-2 cell line system grown on Transwell inserts, and in situ, by single-pass perfusion of rat intestinal segments, jejunum and ileum, in the absence or presence of standard transporter inhibitors or antiretroviral drugs. Atazanavir accumulation by Caco-2 cells was susceptible to inhibition by P-glycoprotein and organic anion transporting polypeptide (OATP) family inhibitors and several antiretroviral drugs (protease inhibitors, TDF). The secretory flux of atazanavir (basolateral-to-apical Papp) was 11.7-fold higher than its absorptive flux. This efflux ratio was reduced to 1.5-1.7 in the presence of P-glycoprotein inhibitors or ritonavir. P-glycoprotein inhibition also resulted in 1.5-2.5-fold increase in atazanavir absorption in situ. Co-administration of TDF, however, reduced atazanavir intestinal permeability by 13-49%, similar to the effect observed clinically. Drug transporters such as P-glycoprotein and OATPs regulate intestinal permeability of atazanavir and may contribute to its poor oral bioavailability and drug-drug interactions with other protease inhibitors and TDF.

Supplementation with 0.1% and 2% vitamin e in diabetic rats: analysis of myenteric neurons immunostained for myosin-V and nNOS in the jejunum

Diabetes mellitus is a disease characterized by hyperglycemia that, when allowed to progress long-term untreated, develops vascular and neurological complications, which are responsible for the development of alterations in the enteric nervous system in diabetic patients. In the gastrointestinal tract, diabetes mellitus promotes motor and sensory changes, and in the reflex function of this system, causing gastroparesis, diarrhea, constipation, megacolon, slow gastrointestinal transit, gastric stasis and dilation with decreased or increased peristaltic contractions. Several studies have shown that oxidative stress is the main responsible for the vascular and neurological complications affecting the enteric nervous system of diabetics. The effects of 0.1% and 2% vitamin E on myosin-V- and nNOS-immunoreactive neurons in the jejunum of diabetic rats were investigated. Thirty rats were divided into the groups: normoglycemic, normoglycemic treated with 0.1% vitamin E, normoglycemic treated with 2% vitamin E, diabetic, diabetic treated with 0.1% vitamin E, and diabetic treated with 2% vitamin E. The neuronal density and areas of neuron cell bodies were determined. Diabetes (diabetic group) significantly reduced the number of myosin-V-immunoreactive neurons compared with the normoglycemic group. The diabetic treated with 0.1% vitamin E and diabetic treated with 2% vitamin E groups did not exhibit a greater density than the D group (P>0.05). Nitrergic density did not change with diabetes (P>0.05). The areas of myosin-V- and nNOS-immunoreactive neurons significantly increased in the normoglycemic treated with 2% vitamin E and diabetic groups compared with the normoglycemic group. Supplementation with 2% vitamin E had a neurotrophic effect only in the area of myosin-V-immunoreactive neurons compared with the diabetic group.

Neuroprotection and neurodegeneration in submucosal VIP-IR neurons in the jejunum of ascorbic acid supplemented aging Wistar rats

The present work studied the effects of ascorbic acid supplementation (1 mg/ml in water daily) on submucosal vasoactive intestinal polypeptide-immunoreactive (VIP-IR) neurons in the jejunum of aging rats. Twenty-five male rats were divided into the following groups: Y90 (young, 90-day-old rats), A345 (aged, 345-day-old rats), A428 (aged, 428-day-old rats), AA345 (ascorbic acid-supplemented rats, 90–345-day old), and AA428 (ascorbic acid-supplemented rats, 90–428-day old). Whole mounts of the submucosal layer were subjected to immunohistochemistry for determination of VIP-IR. Morphometric analyses were carried out in 100 submucosal VIP-IR neuron cell bodies from each group. At 345 days, neurons from supplemented animals were larger than those of non-supplemented animals of the same age. These results indicate that ascorbic acid neutralized free radicals and played a neuroprotective role. At 428 days, no significant differences between cell body areas were seen with or without ascorbic acid supplementation, indicating that, from a certain age onward, the role of ascorbic acid as a VIP-IR antioxidant was reduced. This supposition is supported by the fact that both supplemented and non-supplemented animals had higher blood concentrations of ascorbic acid on Day 428 compared with Day 345. The possible neuroprotective and neurodegenerative effects of ascorbic acid appear to depend on the age of the animals, dose, and its interaction with other antioxidants.

Antihypertensive and Laxative Effects by Pharmacological Inhibition of Sodium-Proton-Exchanger Subtype 3–Mediated Sodium Absorption in the Gut

High intestinal sodium absorption is one mechanism of hypertension and constipation. The sodium-proton-exchanger subtype 3 (NHE3) is an important mediator of sodium absorption in the gut. SAR218034 (SAR) is an orally nonabsorbable specific NHE3 inhibitor. The effect of SAR (1 mg/kg per day in chow) on feces sodium excretion, systolic blood pressure via tail cuff, and gene expression of NHE3 in the gut were studied in senescent lean hypertensive rats (spontaneously hypertensive rats-lean, loaded with NaCl 0.7% in drinking water) and in hypertensive, obese, and hyperinsulinemic rats (spontaneously hypertensive rats-obese, not loaded with NaCl). In spontaneously hypertensive rats-lean, inhibition of intestinal NHE3 by SAR increased feces sodium excretion and reduced urinary sodium excretion, whereas absolute sodium balance and serum sodium concentration were not changed. This suggests reduced intestinal sodium absorption in SAR-treated animals and was associated with increased feces water content (58% versus 42% in placebo treated animals; P=0.0001) and reduction in systolic blood pressure from 222 ± 7 to 198 ± 2 mm Hg (P=0.0001). Angiotensin-converting enzyme inhibition by ramipril plus NHE3 inhibition resulted in an additive blood pressure-lowering effect. In spontaneously hypertensive rats-obese, SAR lowered systolic blood pressure but did not modify serum insulin or cholesterol levels. Gene expression of NHE3 was upregulated in the ileum and colon but not in the jejunum of SAR-treated rats. Reduction of intestinal sodium absorption by selective NHE3 inhibition in the gut reduces high blood pressure and increases feces water excretion. Intestinal NHE3 blockade could be a new treatment strategy for elderly patients suffering from high blood pressure and constipation.

Glucose transporter 2 expression is down regulated following P2X7 activation in enterocytes

With the diabetes epidemic affecting the world population, there is an increasing demand for means to regulate glycemia. Dietary glucose is first absorbed by the intestine before entering the blood stream. Thus, the regulation of glucose absorption by intestinal epithelial cells (IECs) could represent a way to regulate glycemia. Among the molecules involved in glycemia homeostasis, extracellular ATP, a paracrine signaling molecule, was reported to induce insulin secretion from pancreatic β cells by activating P2Y and P2X receptors. In rat's jejunum, P2X7 expression was previously immunolocalized to the apex of villi, where it has been suspected to play a role in apoptosis. However, using an antibody recognizing the receptor extracellular domain and thus most of the P2X7 isoforms, we showed that expression of this receptor is apparent in the top two-thirds of villi. These data suggest a different role for this receptor in IECs. Using the non-cancerous IEC-6 cells and differentiated Caco-2 cells, glucose transport was reduced by more than 30% following P2X7 stimulation. This effect on glucose transport was not due to P2X7-induced cell apoptosis, but rather was the consequence of glucose transporter 2 (Glut2)'s internalization. The signaling pathway leading to P2X7-dependent Glut2 internalization involved the calcium-independent activation of phospholipase Cγ1 (PLCγ1), PKCδ, and PKD1. Although the complete mechanism regulating Glut2 internalization following P2X7 activation is not fully understood, modulation of P2X7 receptor activation could represent an interesting approach to regulate intestinal glucose absorption.

Species Differences in the Antidiarrheal and Antispasmodic Activities of Lepidium sativum and Insight into Underlying Mechanisms

The aim of this study was to see if the crude extract of Lepidium sativum (Ls.Cr) exhibits species specificity in its antidiarrheal and antispasmodic activities along with insight into the underlying mechanisms using the in-vivo and in-vitro experiments. Ls.Cr inhibited castor oil-induced diarrhea in mice at doses (300 and 1000 mg/kg) three times higher dose than for rats. In isolated rat ileum and jejunum, Ls.Cr completely inhibited carbachol (CCh), low K⁺ (25 mM) and high K⁺ (80 mM)-induced contractions, while in guinea-pig tissues, Ls.Cr caused complete inhibition of only CCh-induced contraction. In rabbit tissues, Ls.Cr completely inhibited CCh and low K⁺-induced contractions sensitive to K⁺ channel antagonists. Pretreatment of guinea-pig and rat tissues with Ls.Cr caused a rightward shift in CCh-induced contractions in a pattern similar to dicyclomine, while in rabbit and rat tissues, Ls.Cr shifted isoprenaline curves to the left similar to papaverine. These data indicate that the antidiarrheal and antispasmodic activities of L. sativum are species dependent, mediating its antispasmodic effect through combinations of multiple pathways including activation of K⁺ channels, and inhibition of muscarinic receptors, Ca⁺⁺ channels and PDE enzyme. Rat tissues showed the highest potency. Based on the results, we recommend using multiple species to know the real pharmacological profile of medicinal products.

Mechanisms underlying the antidiarrheal, antispasmodic and bronchodilator activities of Fumaria parviflora and involvement of tissue and species specificity

Ethnopharmacological relevance: In the Greco-Arab (Unani) traditional medicine, Fumaria parviflora Linn. is widely used in hypreractive gut and respiratory disorders including diarrhea, abdominal cramps, indigestion and asthma but scientific studies to provide rational for these medicinal uses are sparse. This study was therefore undertaken to provide ethnopharmacological basis for its medicinal use in diarrhea, abdominal cramps and asthma.Materials and methods: The in vivo studies were conducted in mice and rats while isolated gut and tracheal preparations of rat, guinea-pig and rabbit were suspended in respective tissue baths to measure the isotonic and isometric responses, using Power Lab electronic recorder.Results: The aqueous-methanol extract of Fumaria parviflora (Fp.Cr) protected against diarrhea caused by castor oil in rats and mice, similar to loperamide and dicyclomine, and bronchospasm caused by carbachol (CCh) in rats, similar to aminophylline. In the in vitro studies, Fp.Cr relaxed CCh and isotonic high K+ physiological salts solutions-induced contractions in jejunum, ileum and tracheal preparations of rat, guinea-pig and rabbit. Fp.Cr was predominately more potent against CCh than isotonic high K+ solutions-induced contractions, similar to dicyclomine, suggesting the presence of anticholinergic and calcium channel blocking (CCB) activities, which were confirmed when Fp.Cr shifted the CCh and Ca2+ concentration–response curves, constructed in rat ileum and trachea, towards right. Among intestinal preparations from various species, both anticholinergic and CCB effects of Fp.Cr were exhibited at lower concentrations in rat than the other species. In tracheal preparations, Fp.Cr was the most potent in its CCB effect in rabbit. Within species, CCB effect of Fp.Cr was produced at lower concentrations in rat jejunum than ileum and trachea, whereas, anticholinergic effect was produced at higher concentration in rat trachea than intestine.Conclusion: This study, showing the presence of antidiarrheal, antispasmodic and bronchodilator activities in Fumaria parviflora possibly mediated through dual blockade of muscarinic receptors and Ca2+ channels, provides sound basis for its medicinal uses in diarrhea, abdominal cramps and may be used as bronchodilator in asthma. Species and tissue-dependency of these effects underscores the importance of utilizing multiple tissues and species to get more meaningful results.

Morphological Features of the Lymphoepithelial Structures of the Jejunum after the Stress in Rats

We studied the effect of acute emotional stress on functional status of lymphoid epithelial structures of the jejunum in rats with different behavioral activity. Morphological and functional characteristics of lymphoid tissue were assessed using morphometric, histological and electron microscopic methods. In behaviorally active and passive rats, reduction in villus height, area of the epithelium and lymphoid tissue of the jejunum was recorded on the third day after acute emotional impact. At that, the largest number of destructively modified lymphoid cells was identified by comparison with the other time points. Moreover, destruction of the apical part of the jejunal villi was observed on days 3 and 7 after stress exposure. Recovery of the lymphoepithelial structures of the jejunum after acute stress exposure was detected on day 14.