Inactivation of a diol epoxide by dihydrodiol dehydrogenase but not by two epoxide hydrolases.

The mutagenicity of r-8,t-9-dihydroxy-t-10, 11-oxy-8,9,10,11-tetrahydrobenz[a]anthracene (BA-8,9-diol 10, 11-oxide) toward Salmonella typhimurium TA 100 is not decreased by the presence of large amounts of highly purified microsomal or cytosolic epoxide hydrolase. However, highly purified dihydrodiol dehydrogenase inactivates this diol epoxide, which is a major DNA-binding metabolite of benz[a]anthracene. The K-region epoxide, benz[a]anthracene 5,6-oxide (BA 5,6-oxide) is efficiently inactivated by microsomal epoxide hydrolase, is much less readily inactivated by cytosolic epoxide hydrolase, and is not inactivated by dihydrodiol dehydrogenase. This inactivation of a diol epoxide by dihydrodiol dehydrogenase points to a new significance of this enzyme and a new level of control for diol epoxides.

Arene imines, a new class of exceptionally potent mutagens in bacterial and mammalian cells.

K-region aziridines of polycyclic aromatic hydrocarbons reverted Salmonella typhimurium his- (TA100, TA98) and Escherichia coli trp- strains (WP2 uvrA), without requiring activation by mammalian enzymes. The number of revertants induced per nmol in S. typhimurium TA 100, the most responsive strain, variea from 6 to 10,000 for the seven monoaziridines and the two bisaziridines tested. Interestingly, the mutagenic potencies (y) of the monoaziridines were closely related (r = 0.984) with those of the corresponding epoxide analogues (x) by the equation y = 19.6 X0.97, i.e., the aziridines were about 20-fold stronger mutagens than were the epoxides. One of the aziridines, benzo(a)pyrene (BP)-4,5-imine, was investigated in several additional mutagenicity test systems: toxicity in DNA repair-deficient (rec-) and -proficient (rec+) Bacillus subtilis strains; induction of 6-thioguanine resistance in V79 Chinese hamster cells; and induction of sister chromatid exchanges in cultured human fibroblasts. In all systems, BP-4,5-imine was much more active than the epoxide analogue, BP-4,5-oxide. The difference in activity was particularly large in the two test systems with mammalian target cells in which several hundredfold higher concentrations of the epoxide had to be used in order to elicit equipotent effects. Even r-7,t-8-dihydroxy-t-9,10-oxy-7,8,9,10-tetrahydro-BP, which is one of the most potent mutagens known for V79 cells, was less active in the mammalian cells than was BP-4,5-imine. One reason that arene imines are such potent mutagens may be that they are poorly detoxified. Addition of highly purified microsomal epoxide hydrolase, which strongly reduced the mutagenicity of BP-4,5-oxide and benz(a)anthracene-5,6-oxide in S. typhimurium, had no effect on the mutagenicity of the corresponding aziridines. Furthermore, while benz(a)anthracene-5,6-oxide was inactivated by highly purified cytosolic epoxide hydrolase, benz(a)anthracene-5,6-imine was not inactivated. It is noteworthy that the arene imines are isomeric with and structurally closely related to aromatic amines. Some aziridines derived from nonaromatic structures (ethylene imines) have been reported as metabolites of xenobiotics; others are used as chemotherapeutics. At present, however, the results are mainly of theoretical interest in that a new type of arene derivatives with exceptionally potent, probably ultimate, mutagenicity was discovered and may be exploited for the study of mechanisms of chemical carcinogenesis.

Epoxide hydrolase activity in isolated peroxisomes of mouse liver.

Using trans-stilbene oxide as substrate, the subcellular distribution of epoxide hydrolase was investigated in livers from DBA/2 mice. The highest specific activities were found in cytosolic and light mitochondrial fractions. Isopycnic subfractionation of the light mitochondrial fraction showed that the organelle-bound trans-stilbene oxide hydrolase is localized in peroxisomes.

Induction of cytosolic and microsomal epoxide hydrolases by the hypolipidaemic compound nafenopin in the mouse liver.

The repeated oral administration of nafenopin, a hypolipidaemic compound, at a dose of 100 mg/kg to male C57BL/6, DBA/2, Balb c and C3H mice caused an increase in the specific activity of liver cytosolic epoxide hydrolase, the activity of microsomal epoxide hydrolase was also increased in all except the C3H mice. The dose dependence and the specificity of this induction was investigated in male DBA/2 mice. In the range of 10-200 mg/kg nafenopin the induction of the two hydrolase activities was found to increase with increasing doses of the test compound. Two other cytosolic enzyme activities, lactate dehydrogenase and glutathione S-transferase, remained essentially unchanged within the dose range investigated.

Organ distribution of epoxide hydrolases in cytosolic and microsomal fractions of normal and nafenopin-treated male DBA/2 mice.

Using trans-stilbene oxide and styrene oxide as substrates, epoxide hydrolase activities were measured in cytosolic and microsomal fractions from liver, kidney, heart, lung and testis of male DBA/2 mice. The activities towards these two substrates are remarkably organ specific: trans-stilbene oxide was most effectively hydrolyzed in subcellular fractions from liver, kidney and heart, whereas styrene oxide was predominantly hydrolyzed in those from liver, lung and testis. Immunoblotting experiments were performed with two polyclonal antibodies isolated from goat antisera. Using an anti-mouse liver cytosolic epoxide hydrolase antibody, the corresponding antigen protein was predominantly detected in both cytosolic and microsomal fractions from liver, kidney and heart. An anti-rat liver microsomal epoxide hydrolase antibody proved to be cross-reactive with the mouse enzyme and stained SDS-gels run with microsomal fractions from liver, lung and testis. The anti-mouse liver cytosolic epoxide hydrolase antibody precipitated cytosolic epoxide hydrolase activities from liver, kidney and heart cytosolic fractions. Dietary exposure to the hypolipidemic agent nafenopin (2000 ppm/10 days) caused an induction of trans-stilbene oxide hydrolase and styrene oxide hydrolase activities in cytosolic and microsomal liver fractions whereas, in the other organs, the same activities were unaffected by this treatment. This finding was in accordance with the increased amounts of antigen protein as detected with the antibodies in liver fractions from treated animals. The anti-mouse liver cytosolic epoxide hydrolase antibody was found to precipitate the whole trans-stilbene oxide hydrolase activity also from liver cytosol of nafenopin-treated mice, which indicates the presence of a single cytosolic epoxide hydrolase following induction.

Studies on the mechanism of induction of microsomal cytochrome P452 and peroxisomal bifunctional enzyme mRNAs by nafenopin in primary cultures of adult rat hepatocytes.

The amount of the two mRNAs although lower in cultured hepatocytes than in freshly isolated cells was found to be rapidly inducible upon the addition of 32 microM nafenopin. The induction of cyt.P452 mRNA always preceded the induction of PBE mRNA, but for both, the maximal induction (10-20-fold over control) was obtained within 24 hr and was achieved by transcriptional activation. At early time points (1 and 2 hr after the addition of nafenopin), in the absence of on-going protein synthesis, the amount of cyt.P452 mRNA (and not of PBE mRNA) was transiently higher in the presence of cycloheximide and nafenopin than in the presence of nafenopin alone.

The significance of mouse liver tumor formation for carcinogenic risk assessment: results and conclusions from a survey of ten years of testing by the agrochemical industry.

A survey was performed on the results of 138 carcinogenicity studies conducted in various mouse strains by the agrochemical industry over the period 1983-1993. Data for liver tumor incidence, liver weight, and histopathology were collected along with data on genotoxicity. Studies were judged positive or negative for liver tumor formation on the basis of apparent dose response, malignancy, and difference from historical control values using a weight of evidence approach. Thirty-seven studies were judged to be positive for liver tumorigenicity in one or both sexes. There was no evidence showing an influence of the mouse strain and the duration of the study on the proportion of positive studies. Although 8 of the chemicals tested in the 138 studies were positive in the Ames test, only one of these was judged positive for carcinogenicity. Only 6 of the 37 positive chemicals had any other reported positive genotoxicity findings. A clear relationship between hepatomegaly at 1 year after exposure and a positive tumorigenic outcome at 18 months or 2 years after exposure was demonstrated. Whereas the average relative liver weight of top dose animals was 110% of control in negative studies, it was 150% in positive studies. Likewise, very few negative studies demonstrated significant pathological findings after 1 year, whereas the majority of positive studies had significant liver pathology. The implications of these findings for extrapolation to humans are discussed.

Functional supersensitivity to adrenergic agonists in the rat after DSP-4, a selective noradrenergic neurotoxin.

Rats treated with DSP-4 [N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine], a selective noradrenergic neurotoxin, showed no differences compared to control rats in the number of head dips, a measure of exploratory behavior. Since a previous neurochemical investigation had demonstrated that DSP-4 rats have supersensitive alpha 2- and beta-adrenergic receptors in certain regions of the central nervous system, the behavior of these animals was also examined after the injection of clonidine, an alpha 2 agonist, and clenbuterol, a beta agonist. These drugs reduced, in a dose-dependent manner, the head-dipping of both control and DSP-4 rats. However, this effect was of greater magnitude in DSP-4 animals. Control experiments suggested that the response to clonidine and clenbuterol was mediated centrally by alpha 2 and beta receptors, respectively. Other behavioral experiments with agonists of the dopaminergic and serotoninergic systems indicated that these neurotransmitter systems were unchanged in DSP-4 animals. The results are discussed in terms of the selective action of DSP-4 and the responsiveness of DSP-4 rats to adrenergic agonists. The DSP-4-treated rat may constitute a new model of functional supersensitivity to adrenergic agonists.

Subchronic toxicity study with ethylene-bis-(oxyethylene)-bis-(3-tert-butyl-4-hydroxy-5-methylhydro cin namate) in the cynomolgus monkey: lack of stimulation of the pituitary-thyroid-liver axis.

To evaluate the toxicological profile of the phenolic antioxidant ethylene-bis-(oxyethylene)-bis-(3-tert-butyl-4-hydroxy-5-methyl- hydrocinnamate) (EOC) in a non-human primate, male cynomolgus monkeys (Macaca fascicularis) were treated for 4 weeks by oral administration of 0, 200, or 1000 mg/kg body weight/day. Special attention was directed to parameters of the pituitary-thyroid-liver axis. Moderately increased liver weights and minimal to moderate hepatocellular hypertrophy were observed in treated animals. Otherwise, no treatment-related changes were detected in hematological, clinical chemistry, or urinalysis parameters or upon histopathological examination. Except for a slight induction of microsomal testosterone 16beta-hydroxylation, liver xenobiotic-metabolising enzyme activities and peroxisomal fatty acid beta-oxidation remained unchanged. Likewise, serum levels of thyroid stimulating hormone, thyroxine, 3,3',5-triiodothyronine and 3,3',5'-triiodothyronine as well as 5'-monodeiodinase type 1 mRNA levels in the liver, heart, cerebral cortex, and thyroid were found unchanged. The results demonstrate that, in the Cynomolgus monkey, EOC is only a very weak inducer of liver xenobiotic-metabolizing enzymes and has no effect on thyroid function. In contrast, upon feeding rats at dose levels up to 1000 ppm (equivalent to between 50 and 100 mg/kg body weight/day), EOC has been identified as a strong phenobarbital- and peroxisome proliferator-type inducer of hepatic xenobiotic-metabolizing enzymes, interfering with thyroid hormone homeostasis, causing thyroid follicular hypertrophy, and, upon chronic treatment, inducing thyroid gland follicular cell tumors (Thomas et al., 1995. In Toxicology of Industrial Compounds, pp. 319-339. Taylor and Francis). Thus, the results of this study with EOC in the cynomolgus monkey show that effects of xenobiotics on the pituitary-thyroid-liver axis as frequently observed in rodents can not necessarily be extrapolated to primates including man.

Species differences in the toxicity of p-chloro-o-toluidine to rats and mice. Covalent binding to hepatic macromolecules and hepatic non-parenchymal cell DNA and an investigation of effects upon the incorporation of [3H] thymidine into capillary endothelial cells.

The interaction of p-[14C] chloro-o-toluidine with hepatic macromolecules of rats and mice has been investigated. At all time points after single administration the extent of binding decreased in the order protein greater than RNA greater than DNA in both species. The level of binding to mouse liver DNA was greater than that to rat liver DNA after both single and repeated administration. In vitro studies showed that mouse liver fractions catalysed the binding of p-chloro-o-toluidine to calf thymus DNA more readily than rat liver fractions. Conversely, binding to protein and RNA was more marked in the rat than in the mouse. Species differences in DNA repair rates were not observed. The results failed to demonstrate a preferential persistence of binding to mouse liver nonparenchymal cell DNA. Autoradiographic determinations did not demonstrate any effect of p-chloro-o-toluidine upon the incorporation of [3H] thymidine into subcutaneous capillary endothelial cells. The results suggest that different reactive metabolites are responsible for binding to DNA and protein, and that the pattern of reactive metabolites formed from p-chloro-o-toluidine in the mouse differs from that formed in rats.

Induction of hepatic drug-metabolising enzymes following treatment of rats and mice with chlordimeform.

We investigated the effects of the formamidine insecticide chlordimeform upon the activities of various hepatic drug metabolising enzymes in rats and mice. Chlordimeform treatment induced several enzyme activities. However, the extent of induction depended upon the activity studied, the sex of the animal and the species selected. Microsomal cytochrome P-450 content was elevated in both male and female rats and mice. Ethoxycoumarin O-deethylase activity was induced in male and female rats but not in mice, whilst ethylmorphine N-demethylase activity was elevated in mice, but not in rats. Benzo(a)pyrene hydroxylase activity was increased in female rats and mice, but not in males. UDP-glucuronyl transferase, glutathione S-transferase and microsomal epoxide hydrolase were induced in a dose-dependent manner in male rats, and female rats and mice, but not in male mice.

Lack of covalent binding to DNA of di-n-octyltin dichloride (DOTC) in vivo and in vitro.

[14C]Di-n-octyltin dichloride ([14C]DOTC) was administered by oral gavage to male and female rats. After 96 h hepatic and thymic DNA was isolated. All DNA fractions were radioactive, but analysis of DNA hydrolysates by HPLC revealed that the radioactivity was incorporated via biosynthesis and was not due to adduct formation. The limit of detection for adduct formation, expressed in units of the covalent binding index (CBI = mumol chemical bound per mol nucleotides/mmol chemical applied per kg body wt.) was approximately 0.2 for liver DNA and about 0.7 for thymus DNA. This maximum possible DNA-binding ability is about 30,000 times lower than the corresponding value for the strong carcinogen, aflatoxin B1. In addition, [14C]DOTC did not bind covalently to calf thymus DNA in the presence or absence of rat liver S9 or to DNA of V79 Chinese hamster cells. This study therefore gives no indication for genotoxic activity of DOTC mediated by DNA binding.

Effect of propaquizafop and its free-acid derivative on lauric acid hydroxylation and peroxisomal beta-oxidation in primary cultured rat, mouse, guinea pig and marmoset hepatocytes.

The effects of the phenoxyisopropionic acid derivative propaquizafop and its free-acid derivative on microsomal lauric acid hydroxylase and peroxisomal fatty acyl-CoA beta-oxidation have been investigated in primary cultured hepatocytes obtained from various species and compared with those induced by bezafibrate. The hepatocyte cultures were incubated with these compounds for 48 hr at concentrations between 0.1-100mum. No signs of cytotoxicity were observed as shown by the lack of lactate dehydrogenase (LDH) release into the culture medium. Lauric acid 12-hydroxylase was found to be strongly induced after treatment of rat and mouse hepatocytes with all three compounds, but remained largely unaffected in guinea pig and marmoset hepatocytes. Concomitantly, peroxisomal fatty acyl-CoA beta-oxidation was found to be induced in rat but not in mouse hepatocytes after treatment for 48 hr. However, clearly increased beta-oxidation activities could also be observed in mouse hepatocytes after a 72-hr incubation period. In contrast, only marginally increased beta-oxidation activities were recorded, if at all, in guinea pig and marmoset hepatocytes. The results demonstrate that the effects of propaquizafop and its free-acid derivative in hepatocytes from four species are very similar to those produced by the known peroxisome proliferator (PP) bezafibrate. This is in accordance with the known difference in susceptibility of various species to PP, for example, rats and mice being most responsive whereas guinea pigs and primates including humans are far less responsive or even unresponsive.

The significance of in vitro studies on peroxisome proliferation.

Peroxisome proliferation in rodents is associated with hepatocarcinogenicity. This association has led to increased interest in the phenomenon and to the search for in vitro tests to detect peroxisome proliferators and to study the mechanisms by which proliferation occurs. Primary cultures of adult rat hepatocytes provide such a system: peroxisomal enzymes, cytochrome P-452 and replicative DNA synthesis may all be induced and the response to treatment with many peroxisome proliferators is observed in a manner similar to that in the liver in vivo. Cultured hepatocytes, therefore, provide an optimal system: (i) to screen for potential peroxisome proliferators; (ii) to study structure-activity relationships; (iii) to investigate species differences in the effects of peroxisome proliferators on hepatocytes; and (iv) to study the molecular mechanisms underlying peroxisome proliferation and its relationship to tumour formation.

Increased peroxisomal enzyme mRNA levels in adult rat hepatocytes cultured in a chemically defined medium and treated with nafenopin.

Nafenopin is a known inducer of peroxisome proliferation in the hepatocytes of treated rodents. Primary cultures of adult rat hepatocytes maintained in a chemically-defined medium respond to the drug. RNAs from hepatocyte cultures treated for 1, 8 and 20 hr and their untreated counterparts have been purified and hybridized to radioactive cDNA probes specific for peroxisomal mRNAs (for catalase and the three enzymes of the ß-oxidation system). The amount of the specific mRNAs was fairly constant or increased slightly in control cultures, but increased steadily during treatment of the cultures with a non-toxic dose of nafenopin (32 µm). For the peroxisomal bifunctional enzyme mRNA, representative of the ß-oxidation system, this increase was approximately fivefold after 20 hr, whereas for catalase mRNA a twofold increase compared with the control was observed after 20 hr. The time-course of the induction of the peroxisomal bifunctional enzyme mRNA in vitro was found to be similar to that observed after intragastric treatment of rats with nafenopin. This indicates that mechanistic studies on the early events induced in hepatocytes by peroxisome proliferators can be performed with this culture system. Such studies may help to explain the hepatotoxic/hepatocarcinogenic properties of this class of xenobiotics.

Vasopressors for shock.

BACKGROUND: Besides reversing the underlying cause, the first line treatment for the symptoms of shock is usually the administration of intravenous fluids. If this method is not successful, vasopressors such as dopamine, dobutamine, adrenaline, noradrenaline and vasopressin are recommended. It is unclear if there is a vasopressor of choice, either for the treatment of particular forms of shock or for the treatment of shock in general. OBJECTIVES: To assess the efficacy of vasopressors for circulatory shock in critically ill patients. Our main aim was to assess whether particular vasopressors reduce overall mortality. We also intended to identify whether the choice of vasopressor influences outcomes such as length-of-stay in the intensive care unit and health-related quality of life. SEARCH STRATEGY: We searched MEDLINE, the Cochrane Central Register of Controlled Trials, EMBASE, PASCAL BioMed, CINAHL, BIOSIS, and PsychINFO:all from inception to November 2003; for randomized controlled trials. We also asked experts in the field and searched meta-registries for ongoing trials. SELECTION CRITERIA: We included randomized controlled trials comparing various vasopressors, vasopressors with placebo or vasopressors with intravenous fluids for the treatment of any kind of circulatory failure (shock). Mortality was the main outcome. DATA COLLECTION AND ANALYSIS: Two reviewers abstracted data independently. Disagreement between two reviewers was discussed and resolved with a third reviewer. We used random effects models for combining quantitative data. MAIN RESULTS: We identified eight randomized controlled trials. Reporting of methodological details was for many items not satisfactory: only two studies reported allocation concealment, and two that the outcome assessor was blind to the intervention. Two studies compared norepinephrine plus dobutamine with epinephrine alone in patients with septic shock (52 patients, relative risk of death 0.98, 95% confidence interval 0.57 to 1.67). Three studies compared norepinephrine with dopamine in patients with septic shock (62 patients, relative risk 0.88, 0.57 to 1.36). Two studies compared vasopressin with placebo in patients with septic shock (58 patients, relative risk 1.04, 0.06 to 19.33). One study compared terlipressin with norepinephrine in patients with refractory hypotension after general anaesthesia but there were no deaths (20 patients). REVIEWERS' CONCLUSIONS: The current available evidence is not suited to inform clinical practice. We were unable to determine whether a particular vasopressor is superior to other agents in the treatment of states of shock.

A comparison between topical and infiltrative bupivacaine and intravenous meperidine for postoperative analgesia after inguinal herniorrhaphy.

The purpose of the present study is to compare postoperative analgesia offered by the simple instillation of local anesthetic on the surgical wound, its infiltration with the same local anesthetic, and the use of an intravenous opioid. Sixty patients were divided into the three analgesia groups to be studied: instillation of local anesthetic (Group I), injection of local anesthetic (Group II), and intravenous opioid (Group III). The pain was quantified using the visual analogue scale. It was observed that there was better analgesia in Groups I and II during the first 6 hours postoperatively as compared with Group III (P < 0.0001). At the end of the 12 hours the three modes of analgesia proved comparable. However, after 24 hours there was better analgesic development in Group I, whereas Group II had greater postoperative morbidity. We conclude that the instillation of local anesthesia provides analgesia during the immediate postoperative period comparable to local infiltration using the same anesthetic. Both regional analgesia methods are more effective analgesics during the first 6 hours than are intravenous opioids. Furthermore the simple instillation of local anesthetic allows better analgesic evolution of the surgical wound after the first 24 hours considering the lower rate of resulting complications.

Pancreatic fistula after pancreaticoduodenectomy: a comparison between patients with periampullary tumors and chronic pancreatitis.

BACKGROUND/AIMS: Whether the frequency of anastomotic leak after pancreaticoduodenectomy for benign diseases is greater than for malignant conditions and whether fistula development is associated with surgical mortality remains controversial. The purpose of this study is to compare the incidence of anastomotic leak in patients operated on for chronic pancreatitis and periampullary tumors. METHODOLOGY: The authors retrospectively reviewed the charts of 67 patients (46 males, 21 females, mean age 47 years) submitted to pancreaticoduodenectomy for chronic pancreatitis and periampullary tumors between 1990 and 1996. RESULTS: In 44 patients with periampullary cancers, pancreatic fistula developed in 13 (29%) cases, and in 6 (26%) of the 23 patients with chronic pancreatitis (p>0.05). Of the 19 patients who developed this complication, 5 (26.3%) died, and in the remaining 48 cases, there was only one (2.1%) death (p<0.05). CONCLUSION: The frequency of pancreatic fistula after pancreaticoduodenectomy in patients with periampullary tumors and chronic pancreatitis is not different, but the presence of a fistula is strongly involved in postoperative mortality.

The role of liver transplantation in patients with Caroli's disease.

Caroli's disease, characterized by segmental or diffuse dilation of the intrahepatic biliary ducts, is a rare disease which is difficult to treat. The course of the disorder is characterized by recurrent episodes of cholangitis and hospital stays, with a consequent loss of quality-of-life and productive capacity, often ending in death due to uncontrolled infection. Endoscopic drainage of the bile duct, percutaneously or surgically, is palliative, and presents bad results in the follow-up of these patients. Orthotopic liver transplantation appears to be an effective curative option for the treatment of patients with Caroli's disease associated to complications. The authors present the course of two cases of this disease, associated with congenital fibrosis of the liver worsened by repeated episodes of cholangitis, submitted to orthotopic liver transplantation.

Comparative post-operative study of prostheses, with and without an anti-reflux valve system, in the palliative treatment of esophageal carcinoma.

BACKGROUND/AIMS: Palliative treatment of advanced esophageal carcinoma by esophageal tunnelization with a prosthesis allows immediate relief of dysphagia. However, the procedure is subject to a high rate of morbidity, including gastroesophageal reflux (GER) present in all patients with a prosthesis positioned through the gastroesophageal junction, resulting in complications (pyrosis, aspiration pneumonias, sleep disorders) and reduced quality of life in these patients who already have a lower rate of survival. In an attempt to reduce GER and its complications, the authors created a surgical prosthesis coupled to an anti-reflux valve system, comparing it to the use of an esophageal prosthesis without an anti-reflux valve mechanism. METHODOLOGY: Twenty-two patients were allocated to 2 tunnelization groups: esophageal prosthesis without an anti-reflux valve mechanism (group 1) and surgical prosthesis coupled to an anti-reflux valve system (group 2). The GER was quantified measuring esophageal-gastric pH, and using fluoroscopy, contrast radiographs and esophageal emptying scintigraphy. Initially, the pH of secretions in S1 (esophagus) and S2 (stomach) was determined using reagent strips after aspirating their contents with different syringes. First with the patient seated at rest in bed, later performing a Valsalva maneuver, deep breathing and forced coughing. The same procedure was performed with the patient in left lateral decubitus, right lateral decubitus, and dorsal decubitus with the head of the bed lowered to 20 degrees. After finishing these maneuvers, 15 ml of 1 molar acetic acid were infused through the catheter positioned in the antrum, and, after 5 min, S1 and S2 material sampling was repeated in the same positions as mentioned above. RESULTS: The pH values between the various positions and maneuvers performed in each group separately were not significantly different, but, if we compare the 2 groups, and the secretions obtained in S1 and S2, there was a significant difference in pH measures in all positions. In the patients in group 1, S1 presented a mean pH ranging from 2.87-3.62 in the initial measures, and between 2.17 and 3.5 after the infusion of 15 ml of 1 molar acetic acid. On the other hand, in group 2, the mean pH of S1 remained between 6.34 and 8.32 in the initial measures and between 4.99 and 7.33 in the presence of acid infusion. At the level of S2, the pH remained unchanged between 2 and 2.7, in both groups. CONCLUSIONS: The authors conclude that the association of an esophageal prosthesis with a valve system significantly reduces GER, as compared with its use alone. Furthermore, it allows marked reduction of the symptoms and resulting complications, and does not interfere clinically with esophageal emptying. It thus significantly improves the quality of life of these patients.