Inhibition of intestinal transit by resuscitation-induced gut edema is reversed by L-NIL

Chlamydia muridarum infection differentially alters smooth muscle function in mouse uterine horn and cervix

Chlamydia trachomatis infection is a primary cause of reproductive tract diseases including infertility. Previous studies showed that this infection alters physiological activities in mouse oviducts. Whether this occurs in the uterus and cervix has never been investigated. This study characterized the physiological activities of the uterine horn and the cervix in a Chlamydia muridarum (Cmu)-infected mouse model at three infection time points of 7, 14, and 21 days postinfection (dpi). Cmu infection significantly decreased contractile force of spontaneous contraction in the cervix (7 and 14 dpi; P < 0.001 and P < 0.05, respectively), but this effect was not observed in the uterine horn. The responses of the uterine horn and cervix to oxytocin were significantly altered by Cmu infection at 7 dpi (P < 0.0001), but such responses were attenuated at 14 and 21 dpi. Cmu infection increased contractile force to prostaglandin (PGF_2α) by 53-83% in the uterine horn. This corresponded with the increased messenger ribonucleic acid (mRNA) expression of Ptgfr that encodes for its receptor. However, Cmu infection did not affect contractions of the uterine horn and cervix to PGE₂ and histamine. The mRNA expression of Otr and Ptger4 was inversely correlated with the mRNA expression of Il1b, Il6 in the uterine horn of Cmu-inoculated mice (P < 0.01 to P < 0.001), suggesting that the changes in the Otr and Ptger4 mRNA expression might be linked to the changes in inflammatory cytokines. Lastly, this study also showed a novel physiological finding of the differential response to PGE₂ in mouse uterine horn and cervix.

An implicit discontinuous Galerkin method for modeling acute edema and resuscitation in the small intestine

Edema, also termed oedema, is a generalized medical condition associated with an abnormal aggregation of fluid in a tissue matrix. In the intestine, excessive edema can lead to serious health complications associated with reduced motility. A $7.5\%$ solution of hypertonic saline (HS) has been hypothesized as an effective means to reduce the effects of edema following surgery or injury. However, detailed clinical edema experiments can be difficult to implement, or costly, in practice. In this manuscript we introduce an implicit in time discontinuous Galerkin method with novel adaptations for modeling edema in the 3D layered physiology of the intestine. The model improves over early work via inclusion of the tissue intrinsic storage coefficient, and the effects of Starling overestimation for high venous pressures. Validation against a recent clinical experiment in HS resuscitation of acute edema is presented; the results support the clinical hypothesis that 7.5% HS solution may be effective in the resuscitation of acute edema formation. New results include an improved view into the effects of resuscitation on the hydrostatic pressure profile of edematous rats, effects on lumenal volume attenuation, relative fluid gain and an estimation of the impacts of both acute edema and resuscitation on intestinal motility.

The role of NIGMS P50 sponsored team science in our understanding of multiple organ failure

The history of the National Institute of General Medical Sciences (NIGMS) Research Centers in Peri-operative Sciences (RCIPS) is the history of clinical, translational, and basic science research into the etiology and treatment of posttraumatic multiple organ failure (MOF). Born out of the activism of trauma and burn surgeons after the Viet Nam War, the P50 trauma research centers have been a nidus of research advances in the field and the training of future academic physician-scientists in the fields of trauma, burns, sepsis, and critical illness. For over 40 years, research conducted under the aegis of this funding program has led to numerous contributions at both the bedside and at the bench. In fact, it has been this requirement for team science with a clinician-scientist working closely with basic scientists from multiple disciplines that has led the RCIPS to its unrivaled success in the field. This review will briefly highlight some of the major accomplishments of the RCIPS program since its inception, how they have both led and evolved as the field moved steadily forward, and how they are responsible for much of our current understanding of the etiology and pathology of MOF. This review is not intended to be all encompassing nor a historical reference. Rather, it serves as recognition to the foresight and support of many past and present individuals at the NIGMS and at academic institutions who have understood the cost of critical illness and MOF to the individual and to society.

Gastrointestinal dysmotility disorders in critically ill dogs and cats

OBJECTIVE

To review the human and veterinary literature regarding gastrointestinal (GI) dysmotility disorders in respect to pathogenesis, patient risk factors, and treatment options in critically ill dogs and cats.

ETIOLOGY

GI dysmotility is a common sequela of critical illness in people and small animals. The most common GI motility disorders in critically ill people and small animals include esophageal dysmotility, delayed gastric emptying, functional intestinal obstruction (ie, ileus), and colonic motility abnormalities. Medical conditions associated with the highest risk of GI dysmotility include mechanical ventilation, sepsis, shock, trauma, systemic inflammatory response syndrome, and multiple organ failure. The incidence and pathophysiology of GI dysmotility in critically ill small animals is incompletely understood.

DIAGNOSIS

A presumptive diagnosis of GI dysmotility is often made in high-risk patient populations following detection of persistent regurgitation, vomiting, lack of tolerance of enteral nutrition, abdominal pain, and constipation. Definitive diagnosis is established via radioscintigraphy; however, this diagnostic tool is not readily available and is difficult to perform on small animals. Other diagnostic modalities that have been evaluated include abdominal ultrasonography, radiographic contrast, and tracer studies.

THERAPY

Therapy is centered at optimizing GI perfusion, enhancement of GI motility, and early enteral nutrition. Pharmacological interventions are instituted to promote gastric emptying and effective intestinal motility and prevention of complications. Promotility agents, including ranitidine/nizatidine, metoclopramide, erythromycin, and cisapride are the mainstays of therapy in small animals.

PROGNOSIS

The development of complications related to GI dysmotility (eg, gastroesophageal reflux and aspiration) have been associated with increased mortality risk. Institution of prophylaxic therapy is recommended in high-risk patients, however, no consensus exists regarding optimal timing of initiating prophylaxic measures, preference of treatment, or duration of therapy. The prognosis for affected small animal patients remains unknown.

A comprehensive mathematical framework for modeling intestinal smooth muscle cell contraction with applications to intestinal edema

The contraction of intestinal smooth muscle cells (ISMCs) involves many coordinated biochemical and mechanical processes. In this work, we present a framework for modeling ISMC contractility that begins with chemical models of calcium dynamics, continues with myosin light chain phosphorylation and force generation, and ends with a cell model of the ISMC undergoing contraction-relaxation. The motivation for developing this comprehensive framework is to study the effects of edema (excess fluid build-up in the muscle tissue) on ISMC contractility. The hypothesis is that more fluid equates to dilution of an external stimulis, eventually leading to reduced contractility. We compare our results to experimental data collected from normal versus edematous intestinal muscle tissue.

A mathematical model of intestinal oedema formation

Intestinal oedema is a medical condition referring to the build-up of excess fluid in the interstitial spaces of the intestinal wall tissue. Intestinal oedema is known to produce a decrease in intestinal transit caused by a decrease in smooth muscle contractility, which can lead to numerous medical problems for the patient. Interstitial volume regulation has thus far been modelled with ordinary differential equations, or with a partial differential equation system where volume changes depend only on the current pressure and not on updated tissue stress. In this work, we present a computational, partial differential equation model of intestinal oedema formation that overcomes the limitations of past work to present a comprehensive model of the phenomenon. This model includes mass and momentum balance equations which give a time evolution of the interstitial pressure, intestinal volume changes and stress. The model also accounts for the spatially varying mechanical properties of the intestinal tissue and the inhomogeneous distribution of fluid-leaking capillaries that create oedema. The intestinal wall is modelled as a multi-layered, deforming, poroelastic medium, and the system of equations is solved using a discontinuous Galerkin method. To validate the model, simulation results are compared with results from four experimental scenarios. A sensitivity analysis is also provided. The model is able to capture the final submucosal interstitial pressure and total fluid volume change for all four experimental cases, and provide further insight into the distribution of these quantities across the intestinal wall.

IL-6, TNF-α, and iNOS is associated with decreased colonic contraction in rats with multiple organ dysfunction syndrome

BACKGROUND

Gastrointestinal stasis is frequently accompanied by multiple organ dysfunction syndrome (MODS), which may lead to gastrointestinal smooth muscle dysfunction. The aim of this study is to investigate whether MODS initiates an inflammatory response and produces IL-6, TNF-α, and iNOS cytokines, as well as to determine whether these cytokines give rise to gastrointestinal smooth muscle dysfunction.

MATERIALS AND METHODS

Sixty Wistar rats were divided equally into a negative control group, a positive control group, and a MODS group. The number of stool spots, the contractility of muscle strips in the colon, and morphologic changes to the colon smooth muscle were recorded. The mRNA and protein expressions of IL-6, TNF-α, and iNOS in the colon were detected by semiquantitative reverse transcription polymerase chain reaction and immunohistochemistry respectively. In addition, the NO level was observed.

RESULTS

For the MODS group, the colon stool numbers, maximal contractive stress, and spontaneous frequency of muscle strips were, respectively, 0.77 ± 0.52 pill/h, 301g/cm(3), and 11.52 ± 0.38 contractions/min (P < 0.05); for the negative control group, 1.54 ± 0.64 pills/h, 645 g/cm(3), and 19.2 ± 0.71 contractions/min, respectively (P < 0.05); and for the positive control group, 0.94 ± 0.21 pills/h, 415 g/cm(3), and 14.1 ± 0.52 contractions/min, respectively (P < 0.05). In the MODS group, there was a marked up-regulation of expression of IL-6, TNF-α, and iNOS and the contractility of the smooth muscle strips had a negative correlation with the expression of IL-6, TNF-α, and iNOS.

CONCLUSION

We speculate that reduced colon motility in the MODS rats may be related to the increase in iNOS, IL-6, and TNF-α in the colon muscularis.

Decreased myosin phosphatase target subunit 1(MYPT1) phosphorylation via attenuated rho kinase and zipper-interacting kinase activities in edematous intestinal smooth muscle

BACKGROUND

Intestinal edema development after trauma resuscitation inhibits intestinal motility which results in ileus, preventing enteral feeding and compromising patient outcome. We have shown previously that decreased intestinal motility is associated with decreased smooth muscle myosin light chain (MLC) phosphorylation. The purpose of the present study was to investigate the mechanism of edema-induced decreases in MLC in a rodent model of intestinal edema.

METHODS

Intestinal edema was induced by a combination of resuscitation fluid administration and mesenteric venous hypertension. Sham operated animals served as controls. Contractile activity and alterations in the regulation of MLC including the regulation of MLC kinase (MLCK) and MLC phosphatase (MLCP) were measured.

KEY RESULTS

Contraction amplitude and basal tone were significantly decreased in edematous intestinal smooth muscle compared with non-edematous tissue. Calcium sensitivity was also decreased in edematous tissue compared with non-edematous intestinal smooth muscle. Although inhibition of MLCK decreased contractile activity significantly less in edematous tissue compared with non-edematous tissue, MLCK activity in tissue lysates was not significantly different. Phosphorylation of MYPT was significantly lower in edematous tissue compared with non-edematous tissue. In addition, activities of both rho kinase and zipper-interacting kinase were significantly lower in edematous tissue.

CONCLUSIONS & INFERENCES

We conclude from these data that interstitial intestinal edema inhibits MLC phosphorylation predominantly by decreasing inhibitory phosphorylation of the MLC targeting subunit (MYPT1) of MLC phosphatase via decreased ROCK and ZIPK activities, resulting in more MLC phosphatase activity.

Oxidative stress and ischemia-reperfusion injury in gastrointestinal tract and antioxidant, protective agents

Exacerbation of hypoxic injury after reoxygenation is a crucial mechanism mediating organ injury in transplantation, and in myocardial, hepatic, gastrointestinal, cerebral, renal, and other ischemic syndromes. The occlusion and reperfusion of the splanchnic artery is a useful animal model to elucidate the mechanism of gastrointestinal injury induced by ischemia-reperfusion (I/R). Although xanthine oxidase is a major source of reactive oxygen species (ROS), which plays an important role in the I/R-induced intestinal injury, there are many other sources of intracellular ROS. Various treatment modalities have been successfully applied to attenuate the I/R injury in animal models. This review focuses on the role of oxidant stress in the mechanism of I/R injury and the use of antioxidant agents for its treatment.

Sodium hydrogen exchanger as a mediator of hydrostatic edema-induced intestinal contractile dysfunction

BACKGROUND

Resuscitation-induced intestinal edema is associated with early and profound mechanical changes in intestinal tissue. We hypothesize that the sodium hydrogen exchanger (NHE), a mechanoresponsive ion channel, is a mediator of edema-induced intestinal contractile dysfunction.

METHODS

An animal model of hydrostatic intestinal edema was used for all experiments. NHE isoforms 1-3 mRNA and protein were evaluated. Subsequently, the effects of NHE inhibition (with 5-(N-ethyl-N-isopropyl) amiloride [EIPA]) on wet-to-dry ratios, signal transduction and activator of transcription (STAT)-3, intestinal smooth muscle myosin light chain (MLC) phosphorylation, intestinal contractile activity, and intestinal transit were measured.

RESULTS

NHE1-3 mRNA and protein levels were increased significantly in the small intestinal mucosa with the induction of intestinal edema. The administration of EIPA, an NHE inhibitor, attenuated validated markers of intestinal contractile dysfunction induced by edema as measured by decreased STAT-3 activation, increased MLC phosphorylation, improved intestinal contractile activity, and enhanced intestinal transit.

CONCLUSION

The mechanoresponsive ion channel NHE may mediate edema-induced intestinal contractile dysfunction, possibly via a STAT-3 related mechanism.

Effect of elevated intra-abdominal pressure on the contractile activity and reactivity of smooth muscle tissue from rat gastrointestinal tract to galantamine and drotaverine (No-Spa)

AIM

The aim of the present study was to determine the nature and intensity of changes in the contractile activity and reactivity of gastrointestinal smooth muscle tissue in conditions of increased intra-abdominal pressure.

METHODS

A method for recording isometric contractions of isolated smooth muscle preparations from gastric corpus, duodenum and sigmoid colon of rats was used.

RESULTS

Two groups of rats were used in the study--control animals and animals with elevated abdominal pressure. It was established that pressure of 25 mmHg for 60 min did not cause statistically significant change in the tone and parameters of the spontaneous contractions in all preparation types, as well as in their reactivity to drotaverine (no-spa). Statistically significant increase in the strength of the tonic effects of galantamine (1.10(-6)-1.10(-3) mg/ml) was found in all types of smooth muscles preparations isolated from rats with increased abdominal pressure compared with preparations from the control rats.

CONCLUSIONS

The statistically significant increase in the galantamine-induced effects on smooth muscle preparations is associated with increase in the contractile effectiveness of acetylcholine. M-type cholinergic receptors are predominantly involved in the processes, probably sensibilized from processes activated by the increased intra-abdominal pressure.

A murine model for the study of edema induced intestinal contractile dysfunction

BACKGROUND

We have published extensively regarding the effects of edema on intestinal contractile function. However, we have found the need to expand our model to mice to take advantage of the much larger arsenal of research support, especially in terms of transgenic mouse availability and development. To that end, we have developed and validated a hydrostatic intestinal edema model in mice.

METHODS

Male C57 Black 6 mice were subjected to a combination of high volume crystalloid resuscitation and mesenteric venous hypertension in an effort to induce hydrostatic intestinal edema. Wet to dry ratios, myeloperoxidase activity, mucosal injury scoring, STAT-3 nuclear activation, phosphorylated STAT-3 levels, NF-κB nuclear activation, myosin light chain phosphorylation, intestinal contractile activity, and intestinal transit were measured to evaluate the effects of the model.

KEY RESULTS

High volume crystalloid resuscitation and mesenteric venous hypertension resulted in the development of significant intestinal edema without an increase in myeloperoxidase activity or mucosal injury. Edema development was associated with increases in STAT-3 and NF-κB nuclear activation as well as phosphorylated STAT-3. There was a decrease in myosin light chain phosphorylation, basal and maximally stimulated intestinal contractile activity, and intestinal transit.

CONCLUSION & INFERENCES

Hydrostatic edema in mice results in activation of a signal transduction profile that culminates in intestinal contractile dysfunction. This novel model allows for advanced studies into the pathogenesis of hydrostatic edema induced intestinal contractile dysfunction.

A novel physiologic model for the study of abdominal compartment syndrome (ACS)

BACKGROUND

: Current abdominal compartment syndrome (ACS) models rely on intraperitoneal instillation of fluid, air, and other space-occupying substances. Although this allows for the study of the effects of increased abdominal pressure, it poorly mimics its pathogenesis. We have developed the first reported large animal model of ACS incorporating hemorrhagic shock/resuscitation.

METHODS

: Hemorrhagic shock was induced and maintained (1 hour) in 12 Yorkshire swine by bleeding to a mean arterial pressure (MAP) of 50 mm Hg. The collected blood plus two additional volumes of crystalloid was then reinfused. Mesenteric venous hypertension was induced by tightening a previously placed portal vein snare in a nonocclusive manner to mimic the effects of abdominal packing. Crystalloids were infused to maintain MAP. Hemodynamic measurements, abdominal pressure, peak inspiratory pressures, urine output, and blood chemistries were measured sequentially. Animals were studied for 36 hours after decompression.

RESULTS

: ACS (intra-abdominal pressure of > or =20 mm Hg with new organ dysfunction) developed in all animals. There were significant increases in peak inspiratory pressure, central venous pressure, and pulmonary artery pressure and decreases in MAP upon development of ACS. Urine output was significantly decreased before decompression. Mean blood lactate decreased and base excess increased significantly after decompression.

CONCLUSIONS

: We have created the first reported physiologic animal ACS model incorporating hemorrhagic shock/resuscitation and the effects of damage control surgery.

Evaluating the potential role of nitric oxide as a mediator of hydrostatic edema mediated intestinal contractile dysfunction

BACKGROUND

Administration of L-nil, a selective inhibitor of inducible nitric oxide synthase (iNOS), improves ileus in an animal model of resuscitation induced intestinal edema. The purpose of this study was to elucidate the iNOS/nitric oxide (NO) signal transduction pathway in intestinal edema.

MATERIALS AND METHODS

Male Sprague Dawley rats were divided into two groups; CONTROL and RESUS+VH (edema, 80 cc/kg normal saline (resuscitation) with mesenteric venous hypertension). iNOS mRNA and protein, iNOS activity, NO tissue levels, soluble guanylyl cyclase (sGC) expression, and cyclic guanosine monophosphate (cGMP) levels were measured. As a functional endpoint, we evaluated intestinal contractile strength and frequency in L-nil treated animals.

RESULTS

Edema was associated with increased iNOS mRNA and protein expression without subsequent increases in iNOS activity or tissue NO levels. There was no significant change in sGC expression or increase in cGMP induced by edema. Administration of L-nil did not decrease edema development or preserve contractile strength, but increased contractile frequency.

CONCLUSION

Hydrostatic intestinal edema is not associated with increased iNOS activity or tissue NO levels. Administration of L-nil in edema increases intestinal contractile frequency. This may represent a potential mechanism for the amelioration of ileus seen with the administration of L-nil.

Hydrostatic intestinal edema induced signaling pathways: potential role of mechanical forces

BACKGROUND

Hydrostatic intestinal edema initiates a signal transduction cascade that results in smooth muscle contractile dysfunction. Given the rapid and concurrent alterations in the mechanical properties of edematous intestine observed with the development of edema, we hypothesize that mechanical forces may serve as a stimulus for the activation of certain signaling cascades. We sought to examine whether isolated similar magnitude mechanical forces induced the same signal transduction cascades associated with edema.

METHODS

The distal intestine from adult male Sprague Dawley rats was stretched longitudinally for 2 h to 123% its original length, which correlates with the interstitial stress found with edema. We compared wet-to-dry ratios, myeloperoxidase activity, nuclear signal transduction and activator of transcription (STAT)-3 and nuclear factor (NF)-kappa B DNA binding, STAT-3 phosphorylation, myosin light chain phosphorylation, baseline and maximally stimulated intestinal contractile strength, and inducible nitric oxide synthase (iNOS) and sodium hydrogen exchanger 1-3 messenger RNA (mRNA) in stretched and adjacent control segments of intestine.

RESULTS

Mechanical stretch did not induce intestinal edema or an increase in myeloperoxidase activity. Nuclear STAT-3 DNA binding, STAT-3 phosphorylation, and nuclear NF-kappa B DNA binding were significantly increased in stretched seromuscular samples. Increased expression of sodium hydrogen exchanger 1 was found but not an increase in iNOS expression. Myosin light chain phosphorylation was significantly decreased in stretched intestine as was baseline and maximally stimulated intestinal contractile strength.

CONCLUSION

Intestinal stretch, in the absence of edema/inflammatory/ischemic changes, leads to the activation of signaling pathways known to be altered in intestinal edema. Edema may initiate a mechanotransductive cascade that is responsible for the subsequent activation of various signaling cascades known to induce contractile dysfunction.

Hypertonic saline alters hydraulic conductivity and up-regulates mucosal/submucosal aquaporin 4 in resuscitation-induced intestinal edema

OBJECTIVE

To characterize membrane conductivity by applying mathematical modeling techniques and immunohistochemistry and to localize and predict areas of the bowel where aquaporins may be associated with edema resolution/prevention associated with hypertonic saline. Intestinal edema induced by resuscitation and mesenteric venous hypertension impairs intestinal transit/contractility. Hypertonic saline decreases intestinal edema and improves transit. Aquaporins are water transport membrane proteins that may be up-regulated with edema and/or hypertonic saline.

DESIGN

Laboratory study.

SETTING

University research laboratory.

SUBJECTS

Male Sprague Dawley rats, weighing 270 to 330 g.

INTERVENTIONS

Rats were randomized to control (with and without hypertonic saline) and mesenteric venous hypertension with either 80 mL/kg normal saline (RESUS + VH + VEH) or 80 mL/kg normal saline with hypertonic saline (RESUS + VH + HTS). After 6 hrs, intestinal wet/dry ratios, urine output, peritoneal fluid, and intraluminal fluid were measured. Hydraulic conductivity was calculated from our previously known and published pressure-flow data. The cDNA microarray, Western blot, polymerase chain reaction, and immunohistochemistry studies were conducted for candidate aquaporins and distribution in intestinal edema resolution.

MEASUREMENTS AND MAIN RESULTS

Hypertonic saline decreased edema and increased urine, intraluminal, and peritoneal fluid volume. RESUS + VH favors fluid flux into the interstitium. Hypertonic saline causes increased hydraulic conductivity at the seromuscular and mucosal surfaces at the same time limiting flow into the interstitium. This is associated with increased aquaporin 4 expression in the intestinal mucosa and submucosa.

CONCLUSIONS

Hypertonic saline mitigates intestinal edema development and promotes fluid redistribution secondary to increased membrane conductivity at the mucosal and seromuscular surfaces. This is associated with up-regulation of aquaporin 4 gene expression and protein. Aquaporin 4 may be a useful therapeutic target for strategies to enhance edema resolution.

Postoperative ileus: pathogenesis and treatment

Surgical manipulation of the intestines activates intestinal macrophages that release cytokines and nitric oxide, which results in inhibition of intestinal motility. Subsequent infiltration of circulating leukocytes into the intestinal wall contributes to cytokine and nitric oxide release and exacerbates ileus. Other factors contributing to ileus are endotoxemia; edema of the intestine wall subsequent to excessive fluid therapy; hypocalcemia; and long abdominal incisions. Because treatment of ileus with prokinetic drugs has not proven to be very effective, efforts should be directed at reducing its severity. Strategies which reduce the severity of ileus include pretreatment with a nonsteroidal anti-inflammatory drug, minimizing the length of the abdominal incision, reducing intestinal manipulation, intraoperative lidocaine infusion, correction of hypocalcemia, limiting the volume of intravenous fluids to prevent intestinal edema, and administration of alpha(2) antagonists.

Resuscitation-induced intestinal edema and related dysfunction: state of the science

High volume resuscitation and damage control surgical methods, while responsible for significantly decreasing morbidity and mortality from traumatic injuries, are associated with pathophysiologic derangements that lead to subsequent end organ edema and dysfunction. Alterations in hydrostatic and oncotic pressures frequently result in intestinal edema and subsequent dysfunction. The purpose of this review is to examine the principles involved in the development of intestinal edema, current and historical models for the study of edema, effects of edema on intestinal function (particularly ileus), molecular mediators governing edema-induced dysfunction, potential role of mechanotransduction , and therapeutic effects of hypertonic saline. We review the current state of the science as it relates to resuscitation induced intestinal edema and resultant dysfunction.

Intestinal edema: effect of enteral feeding on motility and gene expression

OBJECTIVE

Edema formation, inflammation, and ileus in the intestine are commonly seen in conditions like gastroschisis, inflammatory bowel disease, and cirrhosis. We hypothesized that early enteral feeding would improve intestinal transit. We also wanted to study the impact of early enteral feeding on global gene expression in the intestine.

DESIGN

Rats were divided into Sham or Edema +/- immediate enteral nutrition (IEN). At 12 h, small intestinal transit via FITC-Dextran and tissue water were measured. Ileum was harvested for total RNA to analyze gene expression using cDNA microarray with validation using real-time PCR. Data are expressed as mean +/- SEM, n = 4-6 and (*), (**) = P < 0.05 versus all groups using ANOVA.

RESULTS

IEN markedly improved intestinal transit with minimal genetic alterations in Edema animals. Major alterations in gene expression were detected in primary, cellular and macromolecular metabolic activities. Edema also altered more genes involved with the regulation of the actin cytoskeleton.

CONCLUSIONS

Intestinal edema results in impaired small intestinal transit and globally increased gene expression. Early enteral nutrition improves edema-induced impaired transit and minimizes gene transcriptional activity.

Hypertonic saline modulation of intestinal tissue stress and fluid balance

Crystalloid-based resuscitation of severely injured trauma patients leads to intestinal edema. A potential mechanism of intestinal edema-induced ileus is a reduction of myosin light chain phosphorylation in intestinal smooth muscle. We sought to determine if the onset of edema initiated a measurable, early mechanotransductive signal and if hypertonic saline (HS) can modulate this early signal by changing intestinal fluid balance. An anesthetized rat model of acute interstitial intestinal edema was used. At laparotomy, the mesenteric lymphatic was cannulated to measure lymph flow and pressure, and a fluid-filled micropipette was placed in the intestinal submucosa to measure interstitial pressure. Rats were randomized into four groups (n=6 per group): sham, mesenteric venous hypertension+80 mL/kg 0.9% isotonic sodium chloride solution (ISCS 80), mesenteric venous hypertension+80 mL/kg 0.9% ISCS+4 mL/kg 7.5% saline (ISCS 80+HS), or 4 mL/kg 7.5% saline (HS alone) to receive the aforementioned intravenous fluid administered over 5 min. Measurements were made 30 min after completion of the preparation. Tissue water, lymph flow, and interstitial pressure were measured. Resultant applied volume induced stress on the smooth muscle (sigmaravi-muscularis) was calculated. Mesenteric venous hypertension and crystalloid resuscitation caused intestinal edema that was prevented by HS. Intestinal edema caused an early increase in intestinal interstitial pressure that was prevented by HS. Hypertonic saline did not augment lymphatic removal of intestinal edema. sigmaravi-muscularis was increased with onset of edema and prevented by HS, paralleling the interstitial pressure data. Intestinal edema causes an early increase in interstitial pressure that is prevented by HS. Prevention of the edema-induced increase in interstitial pressure serves to blunt the mechanotransductive signal of sigmaravi-muscularis.