Segments Of Rat Small Intestine Research Articles

Intestinal grafts grown from stem cells

Gastrointestinal disorders such as Crohn’s disease can lead to a condition known as short bowel syndrome (SBS) in which a significant portion of a person’s small intestine is no longer capable of absorbing nutrients. Intestinal grafts to supplement the remaining small intestine could help restore this lost function. A team led by Harald C. Ott of Massachusetts General Hospital has grown functional intestinal tissue by seeding scaffolds formed from rat small intestines with human pluripotent stem cells (Nat. Commun. 2017, DOI: 10.1038/s41467-017-00779-y). The researchers remove all cells from a segment of rat small intestine to form a scaffold that retains the extracellular architecture of the original tissue. They direct the human stem cells to differentiate into intestinal progenitor cells and then use them to seed the scaffold. After two weeks in culture, the progenitor cells produce many of the cell types usually found in intestinal tissue. The researchers also add

Evaluation of the internalization of AFP-containing noncovalent complexes AIMPILA in the rat model of the isolated segment of rat small intestine

Research is devoted to the study of the ability of the labeled complex «AIMPILA-ACRIDIN» and the test compound «AFP-ACRIDIN» in concentration of 1.0 mkg/ml to internalize in a small intestine. For this purpose there was used the modified technique of the isolated inverted small intestinal sac method in rats with the aid of by ourselves delivered technique with the use of a conjugate of the studied complex with luminescent ACRIDIN in the incubatory environment. The nonspecific luminescence of the incubatory environment without label was shown to be extremely low: the level of a luminescence of 30-39 RLU is the minimum basic signal and can t significantly influence on results of testing. The starting level of a luminescence in the incubatory environment after supplementation of conjugates of AIMPILA-ACRIDIN or AFP-ACRIDIN is rather high and accounts of 1073714 RLU and 1602017, respectively. In a gleam of the «inverted» pieces of a small intestine the level of a luminescence accounted of 548 and 997 RLU and 425-829 RLU. The obtained data allow to consider the complex AIMPILA in rather low concentration is capable to absorb in a small intestine of rat over the physiologically adequate time that similar to AFP labeled by ACRIDIN.

Excised segments of rat small intestine in Ussing chamber studies: A comparison of native and stripped tissue viability and permeability to drugs

Excised rat intestinal tissue mounted in an Ussing chamber can be used for intestinal permeability assessments in drug development. The outer layer of the intestine, the serosa and part of the muscle layer, is traditionally removed since it is considered a barrier to the diffusion of nutrients and oxygen as well as to that of pharmaceutical substances. However, the procedure for removing the serosal-muscle layer, i.e. stripping, is a technically challenging process in the pre-experimental preparation of the tissue which may result in tissue damage and reduced viability of the segment. In this study, the viability of stripped and native (non-stripped) rat small intestine tissue segments mounted in Ussing chambers was monitored and the apparent permeability of the tissue to a set of test compounds across both tissue preparations was determined. Electrical measurements, in particular the potential difference (PD) across the intestinal membrane, were used to evaluate the viability. In this study, there were no differences in initial PD (health status of the tissue) or PD over time (viability throughout the experiment) between native and stripped rat jejunum segments. Overall, there were also no significant differences in permeability between stripped and native rat intestinal tissue for the compounds in this study. Based on these results, we propose that stripping can be excluded from the preparation procedures for rat jejunal tissue for permeability studies when using the Ussing chamber technique.

Ex-vivo absorption study of a nanoparticle based novel drug delivery system of vitamin D3 (Arachitol Nano™) using everted intestinal sac technique

Cholecalciferol, is a fat soluble vitamin D3 (Vit.D3), recognized in promoting bone health in children and adults and also it has other health benefits. Vit.D3 has suggested being dependent on bile salts for the formation of mixed micelles which is a pre requisite for its absorption. The efficiency of oral absorption of conventional Vit.D3 is approximately 50 %. Arachitol Nano™ is a commercially available nanoparticle based novel drug delivery system (NDDS) of Vit.D3. Data on the uptake of Vit.D3 from the NDDS (Arachitol Nano™) through the intestinal epithelium is not documented. The aim of the study was to investigate the absorption of a nanoparticle based NDDS of Vit.D3 (Arachitol Nano™) using everted rat intestinal sac technique. The results of the study suggested that Vit.D3 from Arachitol Nano™ showed a nonspecific absorption through various segments of rat small intestine, with high flux, permeability coefficient and percentage of absorption (79.21 ± 0.23, 76.55 ± 0.24 and 77.73 ± 0.24 % for duodenum, jejunum and ileum). The average absorption of Arachitol Nano™ was 77.83 ± 0.24 % through rat small intestine. The predicted human absorption may be more than 90 %. The study demonstrates that water soluble nanoparticle Vit.D3 (Arachitol Nano™) can substantially increase the oral absorption of the vitamin D3 and thus can be useful in the oral delivery of vitamin D3.

A study of the histological and functional changes of rat small intestinal mucosa in urinary circumstance

Objective To study the histological and functional changes of rat small intestinal mucosa in urinary circumstance for a long period. Methods 22 rats divided into two groups randomly, 12 rats in experiment group accepted bladder substitution operation use 4cm distal small intestine and 10 rats in control group accepted sham operation. 1 month and 5 month postoperation, to observe the histological changes, secretion and absorption changes of the neobladder mucosa, and body weight, blood biochemistry changes of the rats. Results 5 month postoperation, histological hyperplasia happened in neobladder mucosa.the number of goblet cells increased apparently 1 month postoperation and decreased significantly 5 month postoperation.neobladder mucosa showed absorption of water, K+ and NH+4, 1 h absorption were (0.39±0.09)ml,(5.2±0.9)μmol,(7.11±0.87)μmol, respectively;showed secretion of Na+, Cl-, HCO-3, 1 h secretion were(33.2±4.6),(8.0±3.7),(17.7±7.0)μmol, respectively, compared with the data obtained 1 month postoperation, the differences were not significant(P> 0.05).the weight of the residual mucus in the neobladder was(0.091±0.079)g,compared with the data obtained 1 month postoperation, the difference was significant(P 0.05). Conclusion After the rat small intestine mucosa is in contact with urine for a long period, the mucosa shows histological hyperplasia, the number of goblet cells increases in early period, and decreases in later period in this study; significant changes not happen in the mucosa absorption or secretion function of water and electrolyte; the weight of the residual mucus in the neobladder decrease gradually; using 4 cm distal segment of rat small intestine to form bladder substitute, not significantly effect on rat later stage healthy. Key words: Urinary diversion; Small intestinal mucosa

An analysis of cosecretion and coexpression of gut hormones from male rat proximal and distal small intestine.

Gut endocrine cells are generally thought to have distinct localization and secretory products. Recent studies suggested that the cells are highly related and have potential to express more than one hormone. We studied the coexpression and cosecretion of gut hormones in separate segments of rat small intestine. We measured secretion of glucagon-like peptide-1 (GLP-1), peptide YY (PYY), neurotensin, glucose-dependent insulinotropic polypeptide (GIP), and cholecystokinin (CCK) from proximal and distal half of the small intestine, isolated from male rats and perfused ex vivo. Hormone secretion was stimulated by bombesin, the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine, and peptones. Furthermore, tissue samples collected along the intestine were analyzed for expression, hormone content, and cell densities including colocalization. Most hormones responded to all three stimuli (but no GIP response to bombesin). GLP-1 secretion was similar from proximal and distal intestine, whereas PYY was secreted only from the distal half. CCK and GIP were mainly secreted proximally, whereas neurotensin was equally secreted from both parts. Cell densities, hormone concentrations, and expression patterns were generally parallel, with increasing values distally for GLP-1 and PYY, an exclusively proximal pattern for CCK, even distribution for neurotensin and GIP except for the most distal segments. PYY nearly always colocalized with GLP-1. Approximately 20% of GLP-1 cells colocalized with CCK and neurotensin, whereas GLP-1/GIP colocalization was rare. Our findings indicate that two L cell types exist, a proximal one secreting GLP-1 (and possibly CCK and neurotensin), and a distal one secreting GLP-1 and PYY. GIP seems to be secreted from cells that are not cosecreting other peptides.

The Role of Inter-segmental Differences in P-glycoprotein Expression and Activity along the Rat Small Intestine in Causing the Double-peak Phenomenon of Substrate Plasma Concentration

Conflicting results have been reported on segmental differences in expression of P-glycoprotein (P-gp) along the small intestine of animals and humans. In this study, we investigated P-gp mRNA and protein levels within each of nine segments of rat small intestine. In addition, P-gp activity in each segment was evaluated in terms of permeability of rhodamine123 (Rho123), a typical P-gp substrate, using the serial intestinal non-everted sac method. The P-gp mRNA levels tended to increase from the duodenum to the ileum, with peaks in the upper and lower ileum, while P-gp protein level reached its maximum in the middle ileum. The activity of P-gp was also the highest in the middle ileum, and was highly correlated with P-gp protein level. The double-peaked plasma concentration profile that was observed following oral administration of Rho123 to rats could be well reproduced by an intestinal compartmental kinetic model incorporating inter-segmental differences of absorption and excretion rate constants. Our results suggest that the heterogeneous distribution of P-gp along the small intestine plays a key role in causing the double-peak of plasma concentration of P-gp substrates following oral administration to rats.

Use of rat segmental intestine for fetal pancreatic transplantation

It is thought that the small intestine may provide a scaffold for pancreas regeneration. Herein, we investigated whether fetal pancreatic tissue could be transplanted into the segmental intestine in rats. Fetal pancreases from firefly luciferase transgenic Lewis rat embryos (embryonic day 14.5 and 15.5) were transplanted into streptozotocin (STZ)-induced diabetic wild-type Lewis rats. As a scaffold for pancreatic development, rat small intestinal segments were utilized after the removal of mucosa, and fetal pancreases were grafted into the luminal surface through the stoma. We also transplanted fetal pancreases into the omentum. The survival of transplanted fetal pancreases was monitored by luciferase-derived photons and blood glucose levels. Transplanted fetal pancreas-derived photons were stable for 28 days, suggesting that transplanted fetal pancreatic tissues survived and that their intestinal blood supply was maintained.

Membrane Permeability in the Gastrointestinal Tract: The Interplay between Microclimate pH and Transporters

Some examples of pH- and transporter-dependent permeability, determined in side-by-side diffusion cells, are summarized. We investigated the polarized transport in the mucosal-to-serosal direction of monocarboxylic acid-type drugs through the excised rat jejunal tissue and an artificial membrane. We established that, in vitro, these substances are most probably not transported by monocarboxylate transporter 1, but by passive pH-dependent transport. We also studied various influences on the permeability of fluorescein, a low permeability marker, through isolated rat intestinal segments, Caco-2 cell monolayers, and an artificial membrane. Polarized transport of fluorescein in the serosal-to-mucosal direction through the rat jejunum by multidrug resistance-associated protein was triggered by the addition of D-glucose to the mucosal side, while the pH-dependent increase of fluorescein influx is presumably the consequence of a monocarboxylate transporter and a member of the organic-anion transporting polypeptide family. With permeability experiments through the excised segments of rat small intestine, we ascertained that ciprofloxacin is a low-permeability drug and has higher and pH-dependent transport in the mucosal-to-serosal direction than in the opposite direction. We also established that neither the permeability of fluoroquinolones nor their solubility in different buffers was influenced by the interactions with metal cations.

K+-ATP-channel-related protein complexes: potential transducers in the regulation of epithelial tight junction permeability

K(+)-ATP channels are composed of an inwardly rectifying Kir6 subunit and an auxiliary sulfonylurea receptor (SUR) protein. The SUR subunits of Kir6 channels have been recognized as an ATPase, which appears to work as a mechanochemical device like other members of the ABC protein family. Thus, in spite of just gating ions, Kir6/Sur might, in addition, regulate completely different cellular systems. However, so far no model system was available to directly investigate this possibility. Using highly specific antibodies against Kir6.1-SUR2A and an in vitro model system of the rat small intestine, we describe a new function of the Kir6.1-SUR2A complex, namely the regulation of paracellular permeability. The Kir6.1-SUR2A complex localizes to regulated tight junctions in a variety of gastrointestinal, renal and liver tissues of rat, pig and human, whereas it is absent in the urothelium. Changes in paracellular permeability following food intake was investigated by incubating the lumen of morphological well-defined segments of rat small intestine with various amounts of glucose. Variations in the lumenal glucose concentrations and regulators of Kir6.1/SUR2A activity, such as tolbutamide or diazoxide, specifically modulate paracellular permeability. The data presented here shed new light on the physiological and pathophysiological role K(+)-ATP channels might have for the regulation of tight junctions.

Correlation between absorption rates of beta-adrenoreceptor antagonists in rat small intestine and their molecular structures

To study the correlation between the absorption rate constants of beta-adrenoreceptor antagonists in rat small intestinal segments and their molecular structural parameters. The net atomic charges and the molecular volumes of 11 beta-adrenoreceptor antagonists were obtained with the semiempirical self-consistent field molecular orbital calculation CNDO/2 method and Mont Carlo method respectively, using the minimum energy conformation obtained from the optimization of the standard molecular geometry with the molecular mechanics MM+ method. The stepwise multiple regression analysis was used to obtain the correlation equations. The absorption rate constants of beta-adrenoreceptor antagonists in rat jejunum or ileum were well linearly correlated with the sum of the net charges of all hydrogen atoms and the molecular volumes. The beta-adrenoreceptor antagonist with higher lipophilicity, weaker hydrogen-bonding potential,and smaller molecular volume had greater absorption rate constants. The absorption rate constants of beta-adrenoreceptor antagonists in rat small intestinal segments are mainly related with their lipophilicity,hydrogen-bonding potential and molecular size.

A quantitative approach to recording peristaltic activity from segments of rat small intestine in vivo

We have developed methods that allow correlation of propulsive reflexes of the intestine with measurements of intraluminal pressure, fluid movement and spatio-temporal maps of intestinal wall movements for the first time in vivo. A segment of jejunum was cannulated and set up in a Trendelenburg recording system while remaining connected to the vascular and nerve supply of the anaesthetized rat. The resting intraluminal pressure in intact intestine was 2-4 mmHg. Hydrostatic pressures of 2, 4, 8 and 16 mmHg were imposed. At a baseline pressure of 4 mmHg, propulsive waves generated pressures of 9 +/- 1 mmHg, that progressed oral to anal at 2-5 mm s(-1). Individual propulsive waves propelled 0.8 +/- 0.4 mL of fluid. The frequency of propulsive waves increased with pressure, but peristaltic efficiency (mL per contraction) decreased with pressure increase between 4 and 16 mmHg. Atropine, as a bolus, transiently blocked peristalsis, but caused maintained block when infused. Hexamethonium blocked propulsive contractions. Inhibition of nitrergic transmission converted regular peristalsis to non-propulsive contractions. These studies demonstrate the utility of an adapted Trendelenburg method for quantitative investigation of motility and pharmacology of enteric reflexes in vivo.

Effects of an alanyl-glutamine—based oral rehydration and nutrition therapy solution on electrolyte and water absorption in a rat model of secretory diarrhea induced by cholera toxin

Objectives: Recurring diarrhea and persistent diarrhea are commonly associated with malnutrition and long-term functional deficits. A beneficial approach would be to develop an alanyl-glutamine (AlaGln)—based oral rehydration and nutrition therapy (ORNT). We investigated the effect of an AlaGln-ORNT solution on electrolyte and water absorption in a rat model of secretory diarrhea induced by cholera toxin. Methods: Phenolsulfonphthalein (50 μg/mL) was used as a non-absorbable marker for calculation of net water and electrolyte transport. Solutions tested were Ringer’s solution, a glutamine-based ORNT (Gln-ORNT) solution, and an AlaGln-ORNT solution. Cholera toxin (1 μg/mL) was injected into lumen of rat small intestinal segments and incubated for 18 h before the initiation of the perfusion. Results: Cholera toxin induced significant secretion of electrolyte and water in the control Ringer’s solution. AlaGln-ORNT and Gln-ORNT solutions reduced the sodium secretory effect of cholera toxin by 128% and 36%, respectively. The net water secretion also was reduced by 95% and 60%, respectively, with the AlaGln-ORNT and Gln-ORTN solutions. Conclusions: These results showed that AlaGln-ORNT solution can enhance water and electrolyte intestinal absorption even better than glutamine or glucose and thus provide a potential novel approach for ORNT to break the vicious cycle of diarrhea and malnutrition. Clinical trials are now needed in children and adults with diarrhea and malnutrition.

Expression and localization of the multidrug resistance-associated protein 3 in rat small and large intestine

Multidrug resistance-associated protein 3 (MRP3; symbol ABCC3), has been shown to mediate ATP-dependent transport of organic anions including 17beta-glucuronosyl estradiol, glucuronosyl bilirubin, monovalent, and sulfated bile salts. MRP3 mRNA expression was reported in rat intestine suggesting a role of MRP3 in the intestinal transport. We examined the expression and localization of MRP3 in rat small and large intestine by RT-PCR, immunofluorescence, and immunoblot analysis. MRP3 was identified in all intestinal segments by RT-PCR. MRP3 expression was low in duodenum and jejunum but markedly increased in ileum and colon. With the use of a rat MRP3 specific antibody, MRP3 was localized to the basolateral domains of enterocytes. Immunofluorescence analysis and immunoblot analysis confirmed a strong expression of rat MRP3 in ileum and colon. In contrast, MRP2 was predominantly expressed in the proximal segments of rat small intestine. Our findings demonstrate a high expression of rat MRP3 in ileum and colon and provide evidence for an involvement of MRP3 in the ATP-dependent transport of organic anions, including bile salts from the enterocyte into blood.

Secretion of type II phospholipase A2 and cryptdin by rat small intestinal Paneth cells.

We examined the secretion of antimicrobial proteins and peptides into surgically isolated and continuously perfused segments of rat small intestine. Up to nine discrete antimicrobial molecules appeared in the intestinal perfusates following intravenous administration of bethanechol, a cholinergic agonist, or intralumenal instillation of lipopolysaccharide (LPS). Among them were three markers of Paneth cell secretion: lysozyme; type II (secretory) phospholipase A2; and at least one intestinal defensin, RIP-3, that appeared to be an alternatively processed variant of the rat neutrophil defensin RatNP-3. Both bethanechol- and LPS-stimulated intestinal lumenal perfusates (washings) contained molecules that killed Escherichia coli, Salmonella typhimurium, and Listeria monocytogenes in vitro. These molecules were more active against the avirulent S. typhimurium strain 7953S (phoP) than against its virulent parent, S. typhimurium 14028S. These data demonstrate that small intestinal Paneth cells secrete antimicrobial peptides in vivo, that this secretion is regulated by the autonomic (parasympathetic) cholinergic nervous system, and that the release of antimicrobial molecules can be triggered by the presence of bacterial LPS in the intestinal lumen.

Segmental heterogeneity of swelling-induced Cl- transport in rat small intestine.

The effect of cell swelling induced by hypotonic media was studied in segments of rat small intestine. In the Ussing chamber, exposure to a hypotonic medium caused a decrease in short-circuit current (Isc) and potential difference (Vms) in the jejunum, whereas the ileum responded with an increase in Isc and Vms. The transition from one pattern to the other was located about in the middle of the small intestine. Tissue conductance decreased in both segments, probably due to a reduction of paracellular shunt conductance induced by the cell swelling. Voltage scanning experiments revealed that the observed decrease in total tissue conductance in the ileum was caused solely by a decrease in local conductance in the villus region while the crypt conductance did not change, suggesting that the decrease in paracellular conductance of the crypts is compensated by an increase in cellular conductance. The response in both segments was dependent on the presence of Cl- and was blocked by the Cl- channel blocker 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB). It was not affected by the neurotoxin tetrodotoxin. In the jejunum the swelling-induced decrease in Isc was reduced in the presence of the cyclooxygenase inhibitor, indomethacin, or the lipoxygenase inhibitor, nordihydroguaiaretic acid. In the ileum the Cl- secretion induced by hypotonicity was blocked by the K+ channel blocker quinine and was reversed into a decrease in Isc when serosal Ca2+ was zero. We conclude that the observed volume regulatory changes are initiated in the jejunum by an eicosanoid-mediated opening of basolateral Cl- channels and in the ileum by a Ca2+-mediated opening of K+ channels which enhances apical Cl- efflux.

Myenteric denervation of rat jejunum alters calcium responsiveness of intestinal smooth muscle

Background/Aims: Long-term myenteric and extrinsic denervation of a segment of rat jejunum results in increased stress generation by the longitudinal muscle layer of the denervated segment 15 days after denervation. This study examined whether alterations in the properties of either cell membrane calcium channels and/or sarcoplasmic reticular Ca 2+-adenosine triphosphatase (ATPase) contribute to the increased stress development. Methods: The effects of the calcium channel blocker nifedipine and the sarcoplasmic reticular Ca 2+-ATPase inhibitor cyclopiazonic acid on the contractile activity of denervated and control smooth muscle were determined. Results: The ability of nifedipine to inhibit KCl-induced contractions was significantly increased in denervated tissues; however, there was no difference in the potency of nifedipine when tissues were stimulated with carbachol. Calcium concentration-response curves obtained in the presence of either KCl or carbachol were determined in tissues previously depleted of calcium. Long-term denervated tissues showed an increased sensitivity to calcium and a decreased maximum contractile response after stimulation with carbachol. Cyclopiazonic acid inhibited repletion of intracellular calcium stores of control muscle but had no effect in denervated tissue. Conclusions: Long-term denervation of a segment of rat small intestine results in profound alterations in calcium metabolism at the cell membrane and, to a lesser extent, at the sarcoplasmic reticulum of smooth muscle cells of the longitudinal muscle layer.

Regional gastrointestinal absorption of ranitidine in the rat.

Ranitidine absorption from isolated segments of rat small intestine (duodenum, midgut, and terminal ileum) was investigated to examine the influence of pH and 50% bile, and to determine if ranitidine is absorbed preferentially from a specific region. Ranitidine (50 mg/kg) was administered into each segment in pH 5 or pH 7 buffer, or in 50% bile. Venous blood was collected at various times for 40 min from the right jugular vein. When ranitidine was administered in pH 7 buffer or in 50% bile, Cmax and AUC0-40 were significantly greater after administration into the terminal ileum compared to the duodenum and midgut. AUC0-40 was significantly greater when ranitidine was administered in pH 5 buffer or in 50% bile into the duodenum compared to the midgut. Cmax was significantly different between administration into the duodenum and midgut only when ranitidine was administered in 50% bile. Ranitidine administration in pH 5 buffer significantly decreased AUC0-40 and Cmax after administration into the midgut, and AUC0-40 after administration into the terminal ileum compared to administration with pH 7 buffer or in 50% bile. Bile had no significant effect on AUC0-40 after ranitidine administration into the duodenum and midgut compared to administration in pH 7 buffer. However, bile significantly increased AUC0-40 and Cmax after ranitidine administration into the terminal ileum compared to administration with pH 7 and pH 5 buffer. Results suggest that ranitidine is absorbed from the entire small intestine. However, the terminal ileum is the optimal site of gastrointestinal absorption. Furthermore, bile enhances ranitidine absorption from the terminal ileum.

Maltitol-induced increase of transepithelial transport of calcium in rat small intestine.

To gain an insight into a mechanism whereby maltitol increases intestinal absorption of calcium, we evaluated transepithelial calcium transport of everted segments of rat small intestine by comparing the values in the presence of maltitol with the values in the presence of maltose. In jejunal segments, no significant difference in the rate of calcium transport was seen between the incubations in the medium containing 100 mM maltitol and in the medium containing 100 mM maltose, regardless of the calcium concentrations in the mucosal-side medium. By contrast, the everted ileal segments incubated in the presence of maltitol exhibited two-fold greater transepithelial calcium transport than did the segments incubated in the presence of maltose at a high (10 mM) concentration of calcium, whereas at a low (0.5 mM) concentration of calcium, maltitol did not produce a significant effect. With the conditions in which intestinal alpha-glucosidases were inhibited using the medium containing Tris or acarbose, a slight (40%) but significant increase of calcium transport was again observed in the segments incubated in the medium containing maltitol as compared with the medium containing maltose. The results suggest that maltitol enhances the rate of transepithelial calcium transport in the lower part of small intestine by modulating the passive diffusion of calcium, and that not only the nature of low digestibility, but also some other nature(s) of maltitol might be responsible for the maltitol-induced increase of ileal calcium transport.

Determination of a critical level of tissue oxygenation in acute intestinal ischaemia.

Tissue oxygen tension (PtO2) was measured using a miniaturised polarographic oxygen electrode in 134 segments of rat small intestine of varying degrees of ischaemia. Without knowledge of the PtO2 levels, the viability of each segment was scored using clinical parameters and tissue damage scored by independent histological examination. Histologically non-viable bowel had significantly impaired tissue oxygenation when compared with viable bowel (t test, p less than 0.001). Marked degrees of tissue hypoxia were frequently tolerated before major histological damage became apparent, a critical PtO2 level of 1.9 mmHg being identified. The overall accuracy rate of PtO2 measurement in the operative prediction of intestinal viability was 92.5%, which contrasts with a rate of only 57.7% for clinical criteria alone.