Rat Rectum Research Articles

Development of a novel vesicular system using a binary mixture of sorbitan monostearate and polyethylene glycol fatty acid esters for rectal delivery of rutin

Anorectal diseases, such as hemorrhoids, are bothersome benign conditions that warrant special attention. The design of an optimized vesicular system for localized rectal delivery can be a suitable conservative treatment. The feasibility of preparing proniosomes using different types of Gelucires®, in combination with Span® 60 as binary mixtures of nonionic surfactants, was checked, then the prepared proniosomes using Span 60 or Span 60/Gelucire were compared to conventional niosomes through investigations comprising the following: encapsulation efficiency (EE%); particle-size analysis; transmission electron microscopy; zeta potential (Z), and in vitro release study and ex vivo permeation study using excised rat rectum. All preparations showed satisfactory stability (Z >30 mV), particle size <300 nm with niosomes showing the lowest EE%, and the largest particle size, together with the least amount of drug released or accumulated in the rectal walls. Span 60/Gelucire proniosomes exhibited lower particle size as well as better release and permeation results, compared to Span 60 proniosomes. Span 60/Gelucire 44/14 (2:1) proniosomes attained the highest percentage of drug released (98.39%) and drug deposition in the rectal walls (86.26%) after 8 hours, which therefore seems to be the most suitable formula able to achieve targeted therapeutic efficacy, aiming to improve the patient’s quality of life.

Intestinal absorption of sodium cefoxitin in rats: effect of formulation.

The absorption of cefoxitin from rat intestine, rectum and small intestine was greater when the powdered form was administered than when an aqueous solution was given. Cefoxitin absorption from the small intestine was significantly increased after its administration in suppository form prepared with a triglyceride base, although rectal absorption from the suppository did not differ from that of the drug in powdered form. The increase in absorption by the small intestine from the suppository form may be due to fatty acids produced from triglyceride by lipase.

Effects of electroacupuncture on disorder of intestinal motility in a rat model of irritable bowel syndrome

To investigate the effects of electroacupuncture (EA) on intestinal motility disorder in rats with irritable bowel syndrome (IBS) in order to provide experimental evidence for improving clinical treatment to IBS with EA. IBS was induced by inserting a balloon into the rectum of male Sprague-Dawley rats from their neonatal age (8th, 21st day after birth) and applying colorectal distention stimulation by inflating air into the balloon. Peristaltic wave (PW) was used to estimate intestinal motility. Rats were divided into 4 groups (n=6): normal group, untreated group, sham EA group and EA group. Acupoints of Zusanli (ST36) and Shangjuxu (ST37) in the hind limbs bilaterally were chosen for EA and sham EA treatment. Trains of dense-sparse frequencies (100 Hz and 2 Hz alternately) and intensity of 1, 2 and 3 mA (10 min for each) were applied for 30 min with each EA treatment while inserting similar needles without electrical stimulation was done as sham EA treatment. PW recorded for 30 min in normal and untreated groups respectively was taken as control values, while PW recorded after EA or sham EA treatment for 30 min was taken as responsive values. Frequency of PW was significantly increased in the untreated group as compared with that in the normal group (P<0.05), and decreased after 30-min EA treatment (P<0.05). There was no significant change in the PW of sham EA group as compared with the control group and before treatment (P>0.05). These results suggest that 1) there is an abnormal increase in intestinal motility indicating an intestinal motility disorder in IBS rats; 2) EA but not sham EA can relieve such intestinal motility disorder.

Scientific Opinion on the use of calcium lignosulphonate (40–65) as a carrier for vitamins and carotenoids

The Panel on Food Additives and Nutrient Sources added to Food provides a scientific opinion on the safety of calcium lignosulphonate (40–65) when used as a carrier for vitamins and carotenoids intended to be added to foods for colouring and nutrient purposes. Calcium lignosulphonate (40–65) has been evaluated by JECFA and an ADI of 20 mg/kg bw/day was established. Calcium lignosulphonate (40–65) is poorly absorbed following oral administration. From the results obtained in vitro from one bacterial reverse mutation assay and one mammalian chromosomal aberration assay it can be concluded that there is no indication for a genotoxic potential of calcium lignosulphonate (40–65). In a short-term 28-day toxicity study, a NOAEL of 1500 mg/kg bw/day was identified for calcium lignosulphonate (40–65) based on minimal focal/multifocal chronic inflammation in the rectum of male rats. In a 90-day subchronic toxicity study the petitioner identified a NOAEL of 2000 mg/kg bw/day for calcium lignosulphonate (40–65), the highest dose tested. The Panel, however, considered this study inadequate for evaluating the safety of calcium lignosulphonate (40–65) due to the high incidence of lymphoid hyperplasia and lymphoid infiltration in the mandibular and mesenteric lymph nodes, in the Peyer's patches and in the liver in all animals, including controls. Therefore, the Panel considers that available data on calcium lignosulphonate (40–65) are insufficient to establish an ADI. Furthermore, the Panel considers that long-term toxicity studies are needed to elucidate whether the histiocytosis in the mesenteric lymph nodes of the rats observed in the inadequate 90-day toxicity study may progress into a more adverse state with time. Overall, based on the available information, the Panel concludes that the safety of use of calcium lignosulphonate (40–65), as a carrier for vitamins and carotenoids intended to be added to foods for colouring and nutrient purposes, cannot be assessed.

Intrathecal injection of GluR6 antisense oligodeoxynucleotides alleviates acute inflammatory pain of rectum in rats.

To investigate whether the kainate (KA) receptor subunit GluR6 is involved in the acute inflammatory pain. Formalin was injected into the mucosa of rectum in Sprague-Dawley rats to induce visceral pain. The antisense oligodeoxynucleotides (ODNs) of GluR6 were injected once per day for 3 d before formalin injection, after which GluR6 protein level was examined by immunoblotting method. The change of visceral pain was also investigated. The expression of GluR6 in the spinal cord of rats increased after the formalin injection. Moreover, pre-treatment of GluR6 antisense ODNs could suppress GluR6 expression in the spinal cord of rats and decrease the scores of visceral pain at 45 min following formalin injection. Kainate receptor subunit GluR6 plays an important role in the visceral pain induced by injection of formalin into the wall of rectum. GluR6 may serve as a potential target for the treatment of acute inflammatory visceral pain.

Exogenous administration of mesenchymal stem cells ameliorates dextran sulfate sodium-induced colitis via anti-inflammatory action in damaged tissue in rats

Aims Mesenchymal stem cells (MSCs) may modulate inflammatory responses resulting in improvement in inflammatory diseases, as well as tissue regeneration via cellular differentiation. We examined the therapeutic effects of exogenously administered MSCs in dextran sulfate sodium (DSS)-induced colitis in rats. Main methods Experimental colitis was produced in inbred male Lewis rats by administration of 4% DSS in drinking water for 7 days. MSCs (5 × 10 6 cells) which were isolated from whole marrow cells and cultured in an optimal medium for MSC outgrowth were administered to the treated rats via the tail vein on days 0, 2, and 4. On day 7, we evaluated colon length, histological changes, and colonic various mRNA expressions by RT-PCR. Localization of MSCs was evaluated using a green-fluorescent cell linker dye. To evaluate the anti-inflammatory action of MSCs, we assayed LPS-induced TNF-α secretion in a co-culture of MSCs and monocytes (THP-1 cells) using ELISA. Key findings MSCs reduced in bloody stools, weight loss, colon shortening, and microscopic injuries. In the rectum of MSCs-treated rats, mRNA expression of TNF-α, IL-1β, and COX-2 decreased to 40, 15, and 15% of their respective control levels. MSCs significantly suppressed mRNA expression of VEGF, HGF, and b-FGF to 40, 25, and 25% of their respective control levels. Green-fluorescent-labeled MSCs were found only within the lamina propria in inflamed regions. LPS-induced TNF-α secretion by THP-1 cells was significantly suppressed by co-culture with MSCs dose-dependently. Significance We conclude that exogenous MSCs accumulated in inflamed tissues and ameliorated DSS-induced colitis via a local anti-inflammatory action.

Effect of Catharsis on Levels of Plasma Motilin and Vasoactive Intestinal Polypeptide of Rats with Constipation by Outlet Obstruction

Objective To study the effect of catharsis method on the levels of plasma MTL and VIP of OOC rats,and investigate the rationality of purgation and lubricant purgation treating OOC. Methods The models of constipation by outlet obstruction were made by constricting the rectum of rats partly, and taking out stitches in vitro to relieve obstruction.Using the Da Cheng Qi Tang (DCQT) and Ma Ren Wan (MRW) as carrieres to object the effect of catharsis method on the levels of plasma MTL and VIP of rats and contrast histopathologie severity of colitis. Results The inflammatory reaction of intestinal mucous was relieved significantly in DCQT group and MRW group, and levels of plasma MTL were raised significantly than normal group(P＜0.05). The levels of plasma VIP went down significantly in model group, DCQT group and MRW group than in normal group(P＜0.01). Conclusion Purgation and lubricant purgation could relieve the inflammatory reaction of intestinal mucosa of OOC rats, influence the levels of plasm MTL and VIE and promote defecation.But we must consider using them exactly. Key words: Constipation by outlet obstruction (OOC) : Motilin (MTL) : Vasoactive intestinal peptide (VIP):DACHENQITANG (DCQT) ; MARENWAN (MRW) ;

Quantitative analysis of sacral parasympathetic nucleus innervating the rectum in rats with anorectal malformation

Background/Purpose The purpose of this experiment was to identify the neurons in the lumbosacral spinal cord involved in colon-rectal function and to compare normal and anorectal malformation of fetalrats. Methods The authors quantified the sacral parasympathetic nucleus (SPN) innervation of the rectum by Fluorogold (FG) (Fluorochrome, Englewood, CO) retrograde tracing experiment in fetal rats with normal and anorectal malformation. Anorectal malformation was induced in rat fetuses by ethylenethiourea (ETU). The number of FG-labeled SPNs was scored and compared between male fetuses with or without malformation in the ETU-fed group and control groups. Results The number of FG-labeled SPNs in the fetuses without a defect, with ETU injected but without any defects of the anorectum or neural tube, with low-type deformity, and with high-type deformity were (mean ± SEM) 47.3 ± 2.9, 45.6 ± 3.2, 24.2 ± 3.8, and 8.5 ± 2.5, respectively. Fluorogold-labeled SPNs inthe fetuses with high-type deformity were significantly fewer than those in fetuses without defects ( P<.05) and in controls ( P < .05). Conclusions These findings suggest that defective SPN innervation to the rectum is a primary anomaly that coexists with the alimentary tract anomaly in anorectal malformation during fetal development. The intrinsic neural deficiency is an important factor likely to contribute to poor postoperative anorectal function despite surgical correction of the malformation.

High and complementary expression patterns of alcohol and aldehyde dehydrogenases in the gastrointestinal tract

Parkinson's disease (PD) is a heterogeneous movement disorder characterized by progressive degeneration of dopamine neurons in substantia nigra. We have previously presented genetic evidence for the possible involvement of alcohol and aldehyde dehydrogenases (ADH; ALDH) by identifying genetic variants in ADH1C and ADH4 that associate with PD. The absence of the corresponding mRNA species in the brain led us to the hypothesis that one cause of PD could be defects in the defense systems against toxic aldehydes in the gastrointestinal tract. We investigated cellular expression of Adh1, Adh3, Adh4 and Aldh1 mRNA along the rodent GI tract. Using oligonucleotide in situ hybridization probes, we were able to resolve the specific distribution patterns of closely related members of the ADH family. In both mice and rats, Adh4 is transcribed in the epithelium of tongue, esophagus and stomach, whereas Adh1 was active from stomach to rectum in mice, and in duodenum, colon and rectum in rats. Adh1 and Adh4 mRNAs were present in the mouse gastric mucosa in nonoverlapping patterns, with Adh1 in the gastric glands and Adh4 in the gastric pits. Aldh1 was found in epithelial cells from tongue to jejunum in rats and from esophagus to colon in mice. Adh3 hybridization revealed low mRNA levels in all tissues investigated. The distribution and known physiological functions of the investigated ADHs and Aldh1 are compatible with a role in a defense system, protecting against alcohols, aldehydes and formaldehydes as well as being involved in retinoid metabolism.

Changes in plasma diazepan concentration and its anticonvulsant effect after discharge of a diazepam suppository from the rectum in rats

One of the clinical problems regarding the use of suppositories for patients is the discharge of the medication itself after the insertion of the suppository. The effects of the discharge of diazepam (DZP) suppositories from the rectum on the plasma DZP concentration and its anticonvulsant action were investigated in rats. The plasma DZP concentration reached a maximum at approx. 30 min after the rectal administration of a 5 mg/kg DZP suppository. The discharge of the DZP suppository from the rectum at 5 or 10 min after rectal administration significantly reduced the plasma DZP concentration and the anticonvulsant action of the DZP suppository against pentylenetetrazol-induced seizures. However, when the suppository was discharged from the rectum after 20 min, the plasma DZP concentration and the anticonvulsant action were only slightly but not significantly decreased. These results suggest that the discharge of the DZP suppository in the early phase, within 20 min, decreases the plasma concentration and the anticonvulsant action of the DZP suppository in rats. Therefore, when the suppository is discharged from the rectum immediately, sufficient observation and proper treatment are necessary.

Induction and recovery of colonic motility/defecatory disorders after extrinsic denervation of the colon and rectum in rats

Anterior resection for rectal disease is associated with extrinsic autonomic denervation of the neorectum, which may influence the myenteric plexus, and subsequently the motility/defecatory status after operation. A rat model with denervated neorectum was constructed. Colonic contractile activity in vivo, the amount of generic neuron marker (PGP 9.5) and nitric oxide synthase (NOS) were measured periodically. The responses of the muscle strip in each period to electrical field stimulation were evaluated using various neurotransmitters. In rats with denervated neorectum, giant migrating contractions (GMCs) of the distal colon, the number of fecal lumps per day and their small size, significantly increased in the early phase postoperatively, although both recovered in the late-phase period. The contractile response of the muscle strip of the denervated colon to acetylcholine was reduced throughout the period; however, contraction of the denervated colon under the addition of NO inhibitor (l-NAME) was enhanced significantly in the late-phase period, and recovered to the control level by atropine. Neuronal NOS, but not PGP 9.5 concentration, in the myenteric plexus at the distal denervated colon, significantly increased in the late-phase period. None of the above items differed from the control at other colonic portions throughout the period. Extrinsic autonomic denervation causes abnormal hyper-motility in the neorectum, which may be associated with multiple evacuations in the early phase postoperatively. Increased acetylcholine and the subsequent increase of neuronal NOS in the myenteric plexus may be an adaptive mechanism to compensate for such abnormal colonic motility after extrinsic denervation.

生物学的利用能向上を目指したグリチルリチン直腸投与製剤に関する基礎的検討

We investigated the usefulness of a suppository containing highly concentrated glycyrrhizin monoammonium (GZ-NH4) solution prepared by pretreatment with clove oil in rats. The aims of this study were to clarify membrane permeability, the bioavailability of GZ-NH4 and the extent of tissue damage. Membrane permeability was evaluated using Ussing-type diffusion chambers, bioavailability assessed through an in vivo absorption study, tissue damage evaluated through observation of hematoxylin-eosin stained tissues and an in vitro release study was carried out to select the suppository base. The formulations used were a GZ-NH4 solution prepared using phosphate buffered solution (control), GZ-NH4 containing 50% labrasol, and GZ-NH4 pretreated with 2% clove oil at 50°C and 70°C. The GZ-NH4 concentrations of all formulations were set to 50 mg/mL. With the GZ-NH4 pretreated with 2% clove oil formulations, the apparent permeability coefficients (Papp) were 1.7- and 1.9-fold higher, respectively, than that of the control formulation. When the various formulations were applied to the rat rectum at a dose of 50 mg/kg of GZ-NH4, the bioavailability of GZ-NH4 pretreated with 2% clove oil at 70°C was 25%, the highest among the four formulations. In the in vivo absorption study, no damage to the epithelial cells of the rectum was observed. These results suggest that GZ-NH4 pretreated with 2% clove oil at 70°C is the most useful formulation for rectal administration. In the in vitro release study to select suppository base, polyethyleneglycol 1000 (PEG 1000) was selected as the hydrophilic base and Witepsol H-15 as the lipophilic base. The initial release of GZ-NH4 was highest for the Witepsol H-15 suppository base. Overall, our results suggest that a lipophilic suppository containing GZ-NH4 pretreating with 2% clove oil at 70°C has the highest release and absorption rates for GZ-NH4 in rectal administration.

Features of the peritoneal covering of the lesser pelvis with special reference to stomata regions

Occasional reports describe various aspects of the fine morphology of the pelvic peritoneum, but its complete organ characteristics remain undefined. The peritoneal covering of the urinary bladder, rectum, uterus, uterine tube, ovary, broad ligament (BL) and testis in Wistar rats was examined by means of transmission and scanning electron microscopy (TEM, SEM). Unusually complicated relief and stomata between the cubic mesothelial cells characterized the surface of the BL. Deep, parallel furrows separated the wide longitudinal folds over the entire length of the uterine tube. The uterus and the ovary formed less numerous, shallow or extremely deep crypt-like invaginations, as well as serous villus-like or papilla-like evaginations. The flat cells were the predominant cell type over the BL, while the cubic mesothelium was the basic covering of the organs. Most of the cubic cells were located in the invagination of the submesothelial layer (SML). Such cells formed an almost smooth surface over the urinary bladder or formed larger areas of the rectum and the testis surfaces. Numerous microvilli, ciliae, round evaginations and complex lamellar bodies characterized their apical plasmalemma. In conclusion, the mesothelial heterogeneity is a stable feature of the lesser pelvis peritoneum, confirmed by TEM and SEM. The cubic mesothelium characterizes the organ peritoneum, while the BL plays the role of the parietal sheet, involving lymphatic units in the SML. The different types of contacts between the mesothelio-endothelial cells, large lymphatic vessels and occasional stomata are the usual components of the lymphatic units in norm, visible by TEM. Images of stomata, seen by SEM, demonstrate oval-shaped deep channel-like gaps surrounded by cubic mesothelium. The last data extend the evidence on stomata regions, which resemble the diaphragmatic ones. Clusters of cells (macrophages, mastocytes and Lymphocytes), small vessels (blood or lymphatic) and nerve fibers (unmyelinated and rare myelinated) form highly specialized complexes in the SML of the ovary, the uterus and the testis.

Dextrose is absorbed by rectum in hypoglycemic rats

The objective of this study was to determine the efficacy of the rectal administration of dextrose in raising the serum glucose in a hypoglycemic rat model. A randomized, prospective, controlled experimental study was performed using 18-h fasted, acutely anesthetized Harlan Sprague-Dawley rats made hypoglycemic by the intravenous infusion of insulin at 3 U/kg/h for 2 h. At 1 h into the infusion, study rats received 1, 2, or 3 g/kg of 50% dextrose solution infused into the rectum using a balloon tipped catheter. Control animals received an equivolume, equi-osmolar (as compared to the 3 g/kg dose) amount of polyethylene glycol (PEG)-400 by rectum. Blood glucose (BG) measurements were made using blood obtained from the portal vein and a femoral artery. Intravenous insulin administered at 3 U/kg/h consistently produced BG levels 60% of baseline at 60 min and 80% of baseline at 120 min. BG levels in portal and arterial circulation increased after rectal dextrose. In general, portal venous values were greater than arterial after rectal dextrose. The greatest increase was seen 30 min after dextrose by rectum in animals receiving 3 g/kg. A 50% dextrose administered by rectum in hypoglycemic rats is absorbed in quantities sufficient to raise BG in the arterial and portal circulation.

Physicochemical Characterization of Diclofenac Sodium-Loaded Poloxamer Gel as a Rectal Delivery System with Fast Absorption

Rectal poloxamer gel systems composed of poloxamers and bioadhesive polymers were easy to administer to the anus and were mucoadhesive to the rectal tissues without leakage after the dose. However, a poloxamer gel containing diclofenac sodium could not be developed using bioadhesive polymers, since the drug was precipitated in this preparation. To develop a poloxamer gel using sodium chloride instead of bioadhesive polymers, the physicochemical properties such as gelation temperature, gel strength, and bioadhesive force of various formulations composed of diclofenac sodium, poloxamers, and sodium chloride were investigated. Furthermore, the pharmacokinetic study of diclofenac sodium delivered by the poloxamer gel was performed. Diclofenac sodium significantly increased the gelation temperature and weakened the gel strength and bioadhesive force, while sodium chloride did the opposite. The poloxamer gels with less than 1.0% sodium chloride, in which the drug was not precipitated, were inserted into the rectum without difficulty and leakage, and were retained in the rectum of rats for at least 6 hr. Furthermore, poloxamer gel gave significantly higher initial plasma concentrations and faster Tmax of diclofenac sodium than did solid suppository, indicating that drug from poloxamer gel could be absorbed faster than that from the solid one in rats. Our results suggested that a rectal poloxamer gel system with sodium chloride and poloxamers was a more physically stable, convenient, and effective rectal dosage form for diclofenac sodium.

An antagonistic effect of esmolol on beta-3 adrenoceptor in brown adipose tissue in rats.

Esmolol is used in clinical practice as a beta-1 adrenergic antagonist in Europe and North America, but it is still under investigation in Japan. It has a high specificity for beta-1 adrenoceptors relative to the beta-2 subtype. When the antagonizing effect to isoproterenol-induced increase in heart rate (beta-1) or bronchodilation (beta2) is calculated, the ratio of esmolol is reported to be 42.7, which is higher than that of propranolol (0.85) [1]. Based on its high specificity for beta-1 adrenoceptors, esmolol can be used for the treatment of tachycardia in patients with bronchial asthma. Another adrenoceptor subtype, the beta-3 receptor, was found, and its molecular structure was reported by Emorine et al. [2] in 1989. Beta-3 adrenoceptors play roles in thermogenesis, lipolysis, anti-obesity function, and anti-diabetic function, and their genetic variation has been correlated with hereditary obesity and diabetogenesis [3]. Furthermore, their functions in the cardiovascular system have recently been studied [4]. Although the affinities and effects of various drugs affecting beta-adrenoceptors on the beta-3 subtype have been investigated, the effect of esmolol has not been reported, to our knowledge. Beta3 adrenoceptors are distributed in adipose tissues with a high density, and beta-3 adrenergic agonists increase temperature to a greater extent in the interscapular brown adipose tissue than in the rectum in rats [5,6]. In the present study, we investigated the effect of esmolol on the beta-3 adrenoceptors by studying the temperature difference between the interscapular brown adipose tissue and the rectum in rats. The study was approved by our Institutional Animal Care Committee. Forty-five Wistar rats, weighing 200‐300 g, were used. The rats were anesthetized with pentobarbital, 50 mg·kg 1 i.p. A polyethylene catheter (0.9-mm-diameter) was placed in the femoral vein. Thermistor probes were inserted into the interscapular

Modeling volume effects of experimental brachytherapy in the rat rectum: uncovering the limitations of a radiobiologic concept

Purpose: To analyze the significance of volume effects in experimental brachytherapy, based on modeling normal tissue complication probability.Methods and Materials: Experimental brachytherapy in the rat rectum was based on an eight-step 2.5-mm step size source configuration for 192Ir, afterloaded into an unshielded polystyrene applicator. Volume effects were studied using a half-circumferential lead-shielded applicator and a shorter (two-step) source configuration. The main end point was rectal stenosis.Results: Rectal stenosis was always caused by a radiation ulcer. With the shielded configuration, single-dose ED50 (50% incidence of rectal stenosis) increased from 23 Gy to 36.5 Gy. Single-dose ED50 for the short configuration was 77.9 Gy. The data showed a reasonable fit to a three-parameter version of the biophysical model described by Jackson et al. (1995). This model assumes that organs consist of a large number of radiobiologically independent subunits and that radiation causes a complication if the fraction of the organ damaged is greater than its functional reserve. The fraction of the organ damaged is calculated summing over fractions of the organ damaged at each dose level. The calculated mean functional reserve (ν50) of the rat rectum, assuming a cumulative functional reserve distribution in the group of experimental rats, was 0.53.Conclusions: The volume effect observed within small brachytherapy volumes agreed well with clinical experience of large tolerance doses in contact X-ray therapy. However, the ν50 value was comparable to the high functional reserve value reported for liver. Experimental volume effects probably reflect repair processes originating in the areas adjacent to small radiation fields of brachytherapy more than the radiobiologic characteristics of the cells in the irradiated volume.

EFFECT OF CHRONIC ALCOHOL CONSUMPTION ON THE ETHANOL- AND ACETALDEHYDE-METABOLIZING SYSTEMS IN THE RAT GASTROINTESTINAL TRACT

The activities of alcohol dehydrogenase (ADH), catalase, microsomal ethanol-oxidizing system (MEOS) and aldehyde dehydrogenase (ALDH) were measured in gastric, small intestinal, colonic and rectal mucosal samples of rats fed on a liquid alcohol diet for 1 month. In the rectum and large intestine of control animals, the activities of ADH, MEOS and catalase were maximal, whereas the activity of ALDH was minimal. After chronic alcohol intoxication, MEOS activity increased significantly in the stomach. An activation of catalase and MEOS and a decrease of the low-K(M) ALDH activity were observed in the rectum of experimental animals. In rats consuming the alcohol diet, hypertrophy of crypts and an increased number of mitoses were noticed in colonic and rectal mucosa. Acute alcohol intoxication (2 g/kg, intragastrically) produced significantly higher acetaldehyde concentrations in the contents of the large intestine and rectum of rats receiving alcohol chronically compared to controls. Thus, after chronic alcohol intoxication, the large intestine regions showed a greater imbalance between the activities of acetaldehyde-producing and -oxidizing enzymes, which resulted in accumulation of acetaldehyde. This mechanism can account for the local toxicity of ethanol after its chronic consumption, and relates the development of mucosal damage and compensatory hyper-regenerative processes, and possibly carcinogenesis, in the colonic and rectal mucosae of alcoholics to the effects of acetaldehyde.

Selective chemical ablation of the enteric plexus in mice.

Although genetically aganglionic mice such as piebald lethal and lethal spotted mice exhibit striking similarities to the human condition of Hirschsprung's disease (HD), the aganglionic segment is very short and always located in the distal part of the rectum. Topical application of benzalkonium chloride (BAC) to the rectum of rats has been reported to result in segmental aganglionosis. To induce chemical ablation of the enteric plexus in mice to produce an aperistaltic narrow segment simulating HD, 32 mice were divided into three groups: (1) abdominal (n=12), for sigmoid colon treatment; (2) rectal (n=10), for rectum treatment; and (3) controls (n=10). For groups 1 and 2, 0.1% BAC was applied to a 1-cm serosal surface of the bowel for 15 min. In the controls, isotonic saline was applied in this fashion. A detailed histologic examination was performed using hematoxylin and eosin staining and acetylcholinesterase histochemistry. Ten animals (9 in group 1 and 1 in group 2) died 1 to 9 weeks after BAC treatment. Autopsy revealed a narrow segment of bowel at the site of BAC treatment and marked dilatation of the bowel proximal to the narrow segment. The remaining animals were killed 12 weeks after BAC treatment. Histologic examination demonstrated normal myenteric and submucous plexuses in the controls, whereas there was a total lack of innervation in the BAC-treated segments.Topical application of BAC thus successfully produced a narrow aganglionic segment of bowel in normal mice. This model provides the basis for future studies to investigate the pathophysiology of HD and megacolon and for comparison with genetically aganglionic mice.

Inhibitory effect of peptide Epitalon on colon carcinogenesis induced by 1,2-dimethylhydrazine in rats

The effect of synthetic pineal peptide Epitalon (Ala-Glu-Asp-Gly) on colon carcinogenesis was firstly studied in rats. Eighty 2-month-old outbred male LIO rats were subdivided into four groups and were weekly exposed to five subcutaneous injections of 1,2-dimethylhydrazine (DMH) at a single dose of 21 mg/kg body weight. Additionally, 5 days a week, some of the rats were given subcutaneous injections of saline at a dose of 0.1 ml during the whole experiment (group 1, control) or Epitalon at a single dose of 1 μg during the whole experiment (group 2), Epitalon after termination of carcinogen injections (group 3) or during the period of DMH exposure (group 4). Colon carcinomas developed in 90–100% of DMH-treated rats. The number of total colon tumors per rat was 4.1; 2.7; 3.7; 2.9 in groups 1, 2, 3, 4, respectively (the difference in groups 2 and 4 compared with group 1 is significant). In rats from group 2, colon tumors were smaller than in control animals. In group 2, the incidence, as well the multiplicity of tumors in ascending and descending colon, were significantly decreased in comparison with group 1. In group 4, the mean number of tumors per rat was significantly decreased, too. A trend to decrease the number of tumors in the rectum in rats from groups 2, 3 and 4, treated with Epitalon was found. Epitalon inhibited also the development of tumors in jejunum and ileum. Thus, our results demonstrated an inhibitory effect of Epitalon on chemically induced bowel carcinogenesis in rats.