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In addition to a yet-to-be published study showing arabinose to have an inhibiting effect on maltase, in vitro studies have shown l-arabinose to exert an inhibiting effect on small-intestinal sucrase and maltase and the consumption of a sucrose-rich drink containing l-arabinose to exert positive effects on postprandial blood glucose, insulin and C-peptide responses in humans. However, the effects of adding l-arabinose to mixed meals on the indices of glucose control are unknown. The purpose of the present study was to investigate whether the positive effects of l-arabinose added to a sugar drink could be reproduced in subjects consuming a mixed meal containing sucrose and/or starch from wheat flour. A total of seventeen healthy men participated in study 1, a randomised, double-blind, cross-over trial. In this study, the subjects consumed two different breakfast meals containing sucrose and starch from wheat flour (meal A) or starch from wheat flour (meal B) supplemented with 0, 5 and 10 % l-arabinose by weight after a 12 h fast. A total of six healthy men participated in study 2, a randomised, double-blind, cross-over trial. In this study, the subjects also consumed meal B served in two different textures and a liquid meal with maltose supplemented with 0 and 20 % l-arabinose. In addition, 1·5 g of paracetamol was chosen as an indirect marker to assess gastric emptying. Postprandial plasma glucose, insulin and C-peptide concentrations were measured regularly for 3 h. The results of the present study showed that the peak plasma concentration, time to reach peak plasma concentration or AUC values of glucose, insulin and C-peptide were not altered after consumption of the test meals. Overall, it was not possible to reproduce the beneficial effects of l-arabinose added to sucrose drinks when l-arabinose was mixed in a solid or semi-solid mixed meal.

The present in vitro studies report on iron uptake by Caco-2 cells from pepsin and pepsin+pancreatin-digested pork meat proteins at pH values between 4.6 and 7 mimicking conditions in the duodenum and the proximal jejunum, respectively. Heat treatment of the pork meat resulted in increased iron uptake from pepsin-digested samples to Caco-2 cells at pH 4.6. The major enhancing effects on iron uptake by Caco-2 cells were observed after pepsin digestion in the pH range 4.6-6.0, whereas the pepsin+pancreatin-digested samples resulted in negligible iron uptake in Caco-2 cells at pH 7. Thus, the results emphasize the importance of separating pepsin-digested and pepsin+pancreatin-digested proteins during in vitro studies on iron availability. Furthermore, the present results showed the pH dependency of iron uptake anticipated. The enhancing effect of ascorbic acid was verified by increased iron uptake from pepsin-digested pork meat samples at pH 4.6, while no effect of ascorbic acid was observed at pH 7 in pepsin+pancreatin-digested samples.

Limited iron bioavailability is regarded as one of the most confounding factors responsible for low iron absorption and utilisation. In the gastrointestinal lumen of humans and monogastric animals, iron absorption is highly affected by dietary components that decrease or enhance iron availability. This study aims at investigating the matrix effects of lupine and rapeseed products on in vitro non-haem iron availability when included in meat-based diets. In vitro iron availability is measured as Fe(II) dialysability obtained by a method combining in vitro protein digestion and dialysis (IVPD dialysis). Aliquots were collected following digestion with pepsin or pepsin/pancreatin and investigated for their effects on Fe(II) dialysability. Thus, the IVPD imitates the conditions in the duodenum and the proximal jejunum. The method confirms that the major effects on in vitro non-haem iron availability are achieved during duodenal conditions. The results showed a significant enhancing effect of pepsin-digested pork meat on Fe(II) dialysability and a pronounced effect of the plant components on Fe(II) dialysability from meat proteins. Lupine enhances Fe(II) dialysability after pepsin/pancreatin digestion in contrast to rapeseed. Moreover, lupine may constitute a valuable vegetable food component in enhancing iron availability and solubility more distally in the intestine than observed for other enhancers of iron absorption.

Duodenal ulcer (DU) patients have impaired proximal duodenal mucosal bicarbonate secretion at rest and in response to luminal acid with higher acid-stimulated mucosal release of prostaglandin (PG) E2 than healthy subjects. Our purpose was to determine whether this abnormality was present also in the stomach of DU patients.Simultaneous determinations of gastric and duodenal bicarbonate secretion and luminal release of PGE2 were performed in 16 healthy volunteers (5 Helicobacter pylori-positive) and 8 inactive DU patients (all H. pylori-positive).In healthy volunteers the rates of gastroduodenal bicarbonate secretion and the release of PGE2 were not influenced by H. pylori status. In inactive DU patients the rates of basal (704 +/- 84 versus 356 +/- 40 mumol/h; mean +/- SEM) and vagally stimulated (modified sham feeding) (1724 +/- 376 versus 592 +/- 52 mumol/h) gastric bicarbonate secretion were higher (p0.05) than in the health, whereas the corresponding rates (339 +/- 42 versus 591 +/- 51 mumol/h and 543 +/- 99 versus 778 +/- 69 mumol/h) in duodenal bicarbonate secretion were lower (p0.05). In addition, inactive DU patients had higher basal (148 +/- 32 versus 53 +/- 5 ng/h) and stimulated (291 +/- 84 versus 131 +/- 25 ng/h) gastric release of PGE2, but only the basal release of PGE2 into the duodenum was significantly increased (20 +/- 3 versus 5 +/- 1 ng/h; p0.05).Increased mucosal production of PGE2 may be responsible for the abnormally high gastric secretion of bicarbonate in inactive DU patients. The defective duodenal secretion of bicarbonate observed in these patients may be a consequence of previous ulceration rather than the mere presence of H. pylori infection.

The effects of the 5-hydroxytryptamine (5-HT3) receptor antagonist, ICS 205-930 (tropisetron), on basal and 5-HT induced jejunal secretion of water and electrolytes were examined using a double blind, randomised crossover design. In seven healthy volunteers steady state perfusions of the proximal jejunum were performed twice with the Loc-I-Gut tube after 5+5 mg ICS 205-930 or placebo capsules were given. After equilibration for 60 minutes and completion of a 120 minute basal period 5-HT (10 micrograms/kg x min intravenously) was infused for 120 minutes. Net water absorption (mean (SEM)) in the basal period was 0.55 (0.84) ml/cm x h and 0.74 (0.72) ml/cm x h after placebo and ICS 205-930, respectively (p > 0.05). Infusion of 5-HT caused significant net secretion of water after placebo (2.05 (0.58) ml/cm x h; p < 0.02) as well as ICS 205-930 (2.60 (0.89) ml/cm x h; p < 0.05). As ICS 205-930 excerted no effects on either basal or 5-HT induced water and electrolyte transport in the intact human jejunum the compound is probably not efficacious as an anti-secretory drug in patients with 5-HT induced diarrhoea.

To compare the disposition of 5-aminosalicylic acid (5-ASA) and its acetylated metabolite during treatment with olsalazine and mesalazine, 14 patients with inactive ulcerative colitis were randomly assigned to olsalazine (1 g twice daily) and the mesalazines, Asacol (800 + 400 + 800 mg daily), Pentasa (750 + 500 + 750 mg daily), and Salofalk (750 + 500 + 750 mg daily) in a crossover design trial so that all received each drug for seven days. Intraluminal colonic concentrations of 5-ASA were estimated after five days by the method of equilibrium in vivo dialysis of faeces. A predose serum sample and a 24 hour urine collection were obtained on day seven. The 5-ASA and acetyl-5-aminosalicylic acid (Ac-5-ASA) values were determined by high performance liquid chromatography. Olsalazine almost doubled the colonic concentrations (mean 23.7 (SEM) (1.9) mmol/l) of its therapeutically active ingredient (5-ASA) compared with equimolar doses of Pentasa (12.6 (2.2) mmol/l; p less than 0.0003) and Salofalk (15.0 (2.0) mmol/l; p less than 0.003). At the same time, olsalazine treatment was associated with lower serum concentrations and urinary excretions (p less than 0.05) of 5-ASA and Ac-5-ASA compared with the mesalazine preparations. The low systemic load of 5-ASA provided by olsalazine reduces the potential risk of nephrotoxicity during long term treatment.

Lactic acid-fermented foods have been shown to increase Fe absorption in human subjects, possibly by lowering pH, activation of phytases, production of organic acids, or by the viable lactic acid bacteria. In this study the effect of a heat-inactivated lactic acid-fermented oat gruel with and without added viable, lyophilizedLactobacillus plantarum299v on non-haem Fe absorption was investigated. Furthermore, Fe absorption in the distal intestine was determined. In a randomized, double-blinded crossover trial eighteen healthy young women aged 22 (sd3) years with low Fe status (serum ferritin 59Fe and served with two enterocoated capsules (containing55Fe(II) and55Fe(III), respectively) designed to disintegrate in the ileum. The meals were consumed on two consecutive days, e.g. in the order AA followed by BB in a second period. Non-haem Fe absorption was determined from59Fe whole-body retention and isotope activities in blood samples. The concentrations of Fe, lactate, phytate, and polyphenols, and the pH were similar in the heat-inactivated lactic acid-fermented oat gruels with and without addedL. plantarum299v, and no difference in Fe absorption was observed between the test gruels (1·4 and 1·3 %, respectively). Furthermore, no absorption of Fe in the distal intestine was observed. In conclusion, addition of viable, lyophilized lactobacillus to a heat-inactivated lactic acid-fermented oat gruel does not affect Fe absorption, and no absorption seems to occur in the distal part of the intestine from low Fe bioavailability meals in these women.

Lactic acid-fermented foods have been shown to increase Fe absorption in human subjects, possibly by lowering pH, activation of phytases, and formation of soluble complexes of Fe and organic acids. We tested the effect of an oat gruel fermented with Lactobacillus plantarum 299v on nonhaem Fe absorption from a low-Fe bioavailability meal compared with a pasteurised, fermented oat gruel and non-fermented oat gruels. In a crossover trial twenty-four healthy women with a mean age of 25 (SD 4) years were served (A) fermented gruel, (B) pasteurised fermented gruel, (C) pH-adjusted non-fermented gruel, and (D) non-fermented gruel with added organic acids. The meals were extrinsically labelled with 55 Fe or 59 Fe and consumed on 4 consecutive days, for example, in the order ABBA or BAAB followed by CDDC or DCCD in a second period. Fe absorption was determined from isotope activities in blood samples. The fermented gruel with live L. plantarum 299v increased Fe absorption significantly (P, 0·0001) compared with the pasteurised and non-fermented gruels. The lactic acid concentration in the fermented gruel was 19 % higher than in the pasteurised gruel, but the Fe absorption was increased by 50 %. In the gruel with organic acids, the lactic acid concentration was 52 % lower than in the pasteurised gruel, with no difference in Fe absorption. The fermented gruel increased non-haem Fe absorption from a phytate-rich meal in young women, indicating a specific effect of live L. plantarum 299v and not only an effect of the organic acids. Non-haem iron absorption: Phytate: Lactic acid fermentation: Organic acids

A combination of dietary and host-related factors determines iron and zinc absorption, and several in vitro methods have been developed as preliminary screening tools for assessing bioavailability. An expert committee has reviewed evidence for their usefulness and reached a consensus. Dialyzability (with and without simulated digestion) gives some useful information but cannot predict the correct magnitude of response and may sometimes predict the wrong direction of response. Caco-2 cell systems (with and without simulated digestion) have been developed for iron availability, but the magnitude of different effects does not always agree with results obtained in human volunteers, and the data for zinc are too limited to draw conclusions about the validity of the method. Caco-2 methodologies vary significantly between laboratories and require experienced technicians and good quality cell culture facilities to obtain reproducible results. Algorithms can provide semi-quantitative information enabling diets to be classified as high, moderate, or low bioavailability. While in vitro methods can be used to generate ideas and develop hypotheses, they cannot be used alone for important decisions concerning food fortification policy, selection of varieties for plant breeding programs, or for new product development in the food industry. Ultimately human studies are required for such determinations.

A reversed-phase high-performance liquid chromatography (HPLC) method with on-line electrospray ionization/collision-induced dissociation/mass spectrometry (ESI/CID/MS) is presented for the regiospecific analysis of synthetic reference compounds of neutral ether lipids. The reference compounds were characterized by chromatographic retention times, full mass spectra, and fragmentation patterns as an aid to clarify the regiospecificity of ether lipids from natural sources. The results clearly show that single quadrupole mass spectroscopic analysis may elucidate the regiospecific structure of neutral ether lipids. Ether lipid reference compounds were characterized by five to six major ions in the positive ion mode. The 1-O-alkyl-sn-glycerols were analyzed as the diacetoyl derivative, and showed the [M - acetoyl](+) ion as an important diagnostic ion. The diagnostic ions of directly analyzed 1-O-alkyl-2-acyl-sn-glycerols and 1-O-alkyl-3-acyl-sn-glycerols were the [M - alkyl](+), [M + H - H(2)O](+) and [M + H](+) ions. Regiospecific characterization of the fatty acid position was evident from the relative ion intensities, as the sn-2 species had relatively high [M + H](+) ion intensities compared with [M + H - H(2)O](+), whereas the reverse situation characterized the sn-3 species. Furthermore, corresponding sn-2 and sn-3 species were separated by the chromatographic system. However, loss of water was promoted as fatty acid unsaturation was raised, which may complicate interpretation of the mass spectra. The diagnostic ions of directly analyzed 1-O-alkyl-2,3-diacyl-sn-glycerols were the [M - alkyl](+), [M - sn-2-acyl](+) and [M - sn-3-acyl](+) ions. Regiospecific characterization of the fatty acid identity and position was evident from the relative ion intensities, as fragmentation of the sn-2 fatty acids was preferred to the sn-3 fatty acids; however, loss of fatty acids was also promoted by higher degrees of unsaturation. Therefore, both structural and positional effects of the fatty acids affect the spectra of the neutral ether lipids. Fragmentation patterns and optimal capillary exit voltages are suggested for each neutral ether lipid class. The present study demonstrates that reversed-phase HPLC and positive ion ESI/CID/MS provide direct and unambiguous information about the configuration and identity of molecular species in neutral 1-O-alkyl-sn-glycerol classes.

Peptic ulcer disease is overrepresented among smokers; they also heal slowly and relapse frequently. Data are accumulating that smoking is detrimental to gastroduodenal mucosal cytoprotection. This study was designed to assess acute effects of high-dose intragastric nicotine, as it has been shown that nicotine is accumulated in gastric juice when smoking. Seven healthy smokers were given nicotine base (6 mg) as tablets, which yielded very high intragastric concentrations and plasma levels comparable to those seen when smoking. In addition to nicotine analysis, concentration levels of prostaglandin E2 (PGE2), phospholipase A2 (PLA2), and phospholipid classes were measured before and after nicotine administration. Nicotine inhibited PGE2 levels by 27-81%, whereas PLA2 and total phospholipids were unaffected. Lysolecithin, a degradation product of the main constituent of gastric surfactant, ie, phosphatidylcholine, tended to increase, but this was not reflected in intragastric phosphatidylcholine levels. In conclusion, nicotine acutely inhibits PGE2 and may thus impair mucosal cytoprotection. The present findings do not imply a central role of surface-active phospholipids with respect to nicotine and gastric cytoprotection, but the chronic effects of nicotine remain to be investigated.

Prostaglandin analogues of the E-series theoretically offer the ideal antiulcer drugs. Peptic ulcer healing with prostaglandin analogues is, however, no better than would be predicted from their ability to inhibit gastric acid secretion and they are less effective than histamine H2 receptor antagonists in preventing ulcer relapse. It could be that prostaglandin analogues inhibit gastric mucosal synthesis or release of endogenous eicosanoids, thereby abrogating their own effects. This study, therefore, examined how a single therapeutic dose (200 micrograms) of misoprostol, a synthetic analogue of prostaglandin E1, influences gastric mucosal release of endogenous prostaglandin E2 (PGE2), thromboxane B2 (TXB2), and chemotactic leukotriene B4 (LTB4) during basal conditions and in response to gastric luminal acidification (0.1 M HCl; 5 ml/min for 10 minutes). Nine healthy volunteers were studied in a single blind, cross over design. In each subject misoprostol or placebo was instilled in randomised order into the stomach, which was subsequently perfused with isotonic mannitol. Misoprostol significantly decreased basal as well as acid stimulated output of PGE2 and TXB2, without affecting output of LTB4. These data show that misoprostol inhibits gastric mucosal synthesis of prostanoids. Decreased concentrations, or even a changed profile, of native eicosanoids modulating the release of inflammatory mediators from immune cells might explain why prostaglandin analogues have a comparatively poor clinical performance in ulcer healing and prevention.

The selective muscarinic M1 receptor antagonist, pirenzepine, considerably stimulates duodenal mucosal bicarbonate secretion in the rat and increases gastric luminal release of prostaglandin E2 (PGE2) in humans. This study, therefore, looked at the effect of pirenzepine on bicarbonate secretion and luminal output of PGE2 into the stomach and the duodenum of nine healthy volunteers using a new technique permitting simultaneous measurements. In the stomach modified sham feeding increased bicarbonate secretion from 382 (62) mumol/h (mean (SEM)) to 959 (224) mumol/h (p < 0.02). In the duodenum modified sham feeding and acid exposure (HCl 0.1 M; 20 ml; 5 min) of the duodenal bulb increased mucosal bicarbonate secretion from 191 (14) mumol/cm x h to 266 (27) mumol/cm x h (p < 0.02) and 634 (157) mumol/cm x h (p < 0.01), respectively. Pirenzepine (10 mg/h intravenously) reduced basal and vagally stimulated gastric and basal duodenal bicarbonate secretion by about 50% (p < 0.03). In the stomach, but not the duodenum, basal and vagally stimulated PGE2 output increased significantly (p < 0.05) in response to pirenzepine. In conclusion, human gastroduodenal mucosal bicarbonate secretion is regulated by a pirenzepine sensitive mechanism, which is probably cholinergic. The rise in gastric PGE2 output seen in response to M1 receptor inhibition by pirenzepine suggests the existence of a feed back loop secondary to the decrease seen in bicarbonate secretion.

Human cholera is associated with an increased luminal release of prostaglandin E2 (PGE2), but whether inhibition of increased PGE2 synthesis will reduce or control intestinal secretion is uncertain. 'Steady state' perfusions (10 ml/minute) in 12 patients with acute cholera, and repeat perfusions in nine of these patients during the convalescent phase were therefore performed using the triple lumen technique. The proximal jejunum was perfused with isotonic saline containing sodium-sulphobromophthalein as a non-absorbable marker. After intravenous administration of indomethacin (1.0 mg/kg) the jejunal net transfer of fluid and the jejunal flow rate of PGE2 were determined in 30 minute periods for 120 minutes after a 120 minute control period. Indomethacin decreased net fluid secretion (2.1 (0.3-4.2) v 4.5 (2.5-8.4) ml/hour x cm; medians, Q50 ranges, p less than 0.01) and the jejunal flow rate of PGE2 (1.5 (1.2-2.7) v 2.2 (1.4-4.9) ng/minute, p less than 0.05). The results of similar perfusion studies in 22 patients with acute cholera, used to establish the spontaneous time related change in fluid secretion, showed no significant change in net fluid transfer (3.5 (2.2-6.2) to 3.5 (2.6-11.6) ml/hour x cm, p greater than 0.25) over 240 minutes. These data provide further evidence in favour of the hypothesis that prostaglandins have a role in the cholera toxin induced intestinal fluid secretion in man.

The influence of oral carbenoxolone sodium (50 mg X 3 daily) on prostaglandin E2 release into gastric juice has been examined in nine peptic ulcer patients (duodenal ulcer, n = 6; prepyloric ulcer, n = 1; gastric ulcer, n = 2) during modified sham feeding and following bolus stimulation of acid secretion by pentagastrin (6 micrograms/kg). Carbenoxolone increased the overall mean of prostaglandin E2 concentrations in gastric juice following modified sham feeding by 32 +/- 9% (mean +/- SEM; P less than 0.02) and decreased the acidity slightly but significantly (P less than 0.05). A marked rise in prostaglandin E2 levels (46 +/- 11%; n = 5; P less than 0.02) was observed in for duodenal ulcer patients and the patient with a prepyloric ulcer responding to therapy (i.e., pain relief and ulcer healing within 4 weeks of treatment). A significant peak (P less than 0.05) related to modified sham feeding was observed only during medication, while a late gradual increase in prostaglandin E2 levels--not associated with vagal stimulation--occurred both in control and carbenoxolone experiments. No significant differences were observed following pentagastrin stimulation. The initial peak in prostaglandin E2 levels observed during medication favours the notion that the mechanism of drug action relies on inhibition of enzymatic degradation while the late increase in prostaglandin E2 levels may be explained by artificial prostaglandin formation during the aspiration procedure.

The elimination of [3H]prostaglandin E1, in anaesthetized rats was studied by continuous intravenous or intraarterial infusions, producing steady-state concentrations at the level of endogenous prostaglandin E2 in mixed venous blood. Blood samples (0.5 ml) were collected from the carotid artery or the right atrium, respectively. The levels of [3H]prostaglandin E1 were measured at different infusion time intervals and the 3H-labeled hydrophobic metabolites characterized. Cardiac output was estimated by a modification of the dye injection method, using 125I-labelled albumin as the marker. From the cardiac output and the rate of infusion, the fractional clearance of the lung and the systemic beds in the steady-state situation were estimated to 88.3 ± 3.2% and 54.1 ± 15.2%(mean ± S.D.), respectively. The hydrophobic metabolites were characterized chromatographically on Sephadex LH-20 columns, using synthetically prepared [14C]prostaglandin metabolites as internal standards and markers. The identities of some metabolites were further established by derivative formation to a constant [3H]/[14C] ratio. The major metabolite was 15-keto-13,14-dihydro-[3H]prostaglandin E1, while 15-keto-[3H]prostaglandin E1 and 13,14-dihydro-[3H]prostaglandin E1 could not be demonstrated.

Azodisal sodium is a highly effective means of oral delivery of 5-amino-salicylic acid to the colonic mucosa. Administration of this drug to patients intolerant of sulphasalazine, however, occasionally results in liquid stools. In preliminary experiments, which comprised 10 healthy volunteers treated with colectomy for ulcerative colitis, ileostomy fluid output increased (p less than 0.001) during oral intake of azodisal sodium (1 g/day). In a double blind, placebo controlled crossover study, comprising eight similar volunteers, ileostomy fluid output increased (p less than 0.05) in a dose related manner during intake of azodisal sodium (1 g/day vs 2 g/day) compared with placebo or sulphasalazine (2 g/day). Concentrations of prostaglandin (PG)F2 alpha in free ileal water determined by equilibrium in vivo dialysis of ileostomy contents decreased (p less than 0.05) during intake of azodisal sodium (2 g/day), whereas concentrations of PGE2 and the output of PGE2, PGF2 alpha, and 'PGE2 + PGF2 alpha' remained unchanged. Thus increased formation of PGs is apparently not the cause of increased ileostomy fluid output associated with azodisalicylate intake.

The diarrhea of cholera is considered to rely solely on a cyclic adenosine monophosphate-mediated secretory mechanism. However, both 5-hydroxytryptamine and prostaglandin E2 have been proposed to be involved in the pathogenesis of cholera. In vivo experiments were performed, therefore, in the rat jejunum to investigate the influence of purified cholera toxin on fluid secretion, luminal release of 5-hydroxytryptamine and prostaglandin E2, and formation of mucosal cyclic adenosine monophosphate. Also the effects of ketanserin, indomethacin, verapamil, and nifedipine on the named parameters were studied. Cholera toxin dose-dependently (0.1-0.5 microgram/ml) and time-dependently (1-5 h) increased mean net fluid secretion with a maximum response at 4 h. It also caused a significant (p less than 0.01) rise in release of 5-hydroxytryptamine and prostaglandin E2, in addition to formation of cyclic adenosine monophosphate. The dose-response curve for cholera toxin-induced fluid secretion was shifted to the right by indomethacin (10 mg/kg s.c.) and ketanserin (200 micrograms/kg s.c.), none of which caused a change in cholera toxin-induced release of 5-hydroxytryptamine. However, both agents significantly decreased the release of prostaglandin E2. Verapamil (0.2-9.5 micrograms/min i.a.) and nifedipine (0.05-0.5 microgram/min i.a.) dose-dependently reduced cholera toxin-induced fluid secretion. The estimated local concentrations at half-maximal inhibition were 5 x 10(-7) M verapamil and 5 x 10(-8) M nifedipine, respectively. The cholera toxin-induced increase in release of 5-hydroxytryptamine and prostaglandin E2 and formation of cyclic adenosine monophosphate was unaffected by verapamil. These results support the concept that cholera toxin-induced fluid secretion in vivo is caused, in part, by release of 5-hydroxytryptamine, which in turn stimulates formation of prostaglandin E2.

Studies in the rat jejunum in vivo have shown that 5-hydroxytryptamine (5-HT) causes secretion of fluid and luminal release of prostaglandin (PG) E2. These effects can be blocked by indomethacin and ketanserin, which suggests that PGE2 may be an important intermediate in the transduction mechanism leading to 5-HT induced fluid secretion. To test this hypothesis in man 'steady state' perfusions (9 ml/min) were done in eight healthy volunteers using the triple lumen technique. The proximal jejunum was perfused with Ringer's solution which contained 51Cr-EDTA as a non-absorbable marker. Before and after the administration of indomethacin (1.0 mg/kg iv) the effects of exogenous 5-HT (10 micrograms/kg/min iv) on jejunal net transport of fluid and electrolytes and jejunal flow rate (JFR) of PGE2 were measured in 15-min periods for 2 x 60 minutes after a 60 minute control period. 5-HT reversed fluid and electrolyte absorption into profuse secretion (p less than 0.01, Duncan's multiple range test) and significantly increased JFR of PGE2 (p less than 0.01). Indomethacin partly restored fluid and electrolyte absorption (p less than 0.01) and inhibited JFR of PGE2 (p less than 0.05). These results provide further evidence in favour of the theory that PGs are involved in 5-HT induced intestinal fluid secretion.

Sephadex LH 20 columns have been investigated for the separation of initial prostaglandin metabolites. Solvent systems are described for the separation of the free acids of 15-keto-dihydro-PGE1, 15-keto-PGE1, PGE1, and PGF1alpha. Further, one of the solvent systems is described for the separation of pulmonary metabolites of PGE1 and PGF1alpha, and another one for separation of dihydro-PGE1 and PGE1.

Inhibition of ion transport by exogenous prostaglandins (PGs) has previously been accomplished only by using "pharmacologic" doses (10 −7 –10 −4 M). Therefore, experiments were performed in which the in vitro effects of low (physiologic) doses (10 −11 –10 −7 M) were assessed in the Ussing chamber preparation of human jejunal mucosa, both with and without blockade of endogenous PG-production by indomethacin (2.9 × 10 −5 M). Serosal application of PGE 2 caused a prompt, dose-dependent rise in short-circuit current (I sc ), decreased net Na flux (J net Na ), elicited Cl secretion, and slightly depressed conductance (G). Dose-response curves for the early effects on I sc and J net Na were performed. The percentage maximal response (R max ) and the concentration for half-maximal response ( k m ) were determined by nonlinear regression analysis using the normal Michaelis-Menten function (iterative evaluation by "least squares"). In the presence of indomethacin, the threshold concentration for effect of PGE 2 was 10 −10 M; R max : stimulation by 26% and inhibition by 58% of control values; and k m : 10 −9 M and 0.7 × 10 −9 M for I sc and J net Na , respectively. In the absence of indomethacin, the threshold concentration for exogenous PGE 2 was 10 −9 M; R max : stimulation by 15% and inhibition by 46% of control values; and k m 4.7 × 10 −8 M and 1.2 × 10 −8 M for I sc and J net Na , respectively. The mean concentration of endogenous PGE 2 released into the serosal bath was approximately 2 × 10 −11 M for indo-methacin-blocked tissues, and 1.8 × 10 −9 M for unblocked tissues. The clearance of exogenous PGE 2 from the serosal bath was about 20% during the experimental period, while less than 1% diffused across the membrane into the mucosal bath. The initial rise in I sc rapidly declined so that PGE 2 had a transient effect that cannot be explained by clearance of PGE 2 , but is rather probably due to the activation of self-controlling feedback mechanisms in the tissue. Since J m−s Na and G during control periods were higher with indomethacin blockade than without, and since I sc during experimental periods with high PGE 2 concentrations usually reached a stable level above baseline before the effect dissipated, PGE 2 appeared to have a "steady-state" effect as well, although less sensitive. Similar responses in I sc and J net Na , were observed following mucosal PGE 2 application, but required concentrations larger than 10 −8 M. PGF 2α had no effect on ion transport up to a concentration of 10 −7 M. In conclusion, suppression of PG-biosynthesis by indomethacin increased the initial sensitivity of the tissue to exogenous PGE 2 . The extremely low dose-response suggests a "true" physiologic role for PGs in the modulation of intestinal ion transport. Since k m of the response to PGE 2 appeared to be below the threshold for activation of the intestinal adenylatecyclase-cAMP system, the role of cAMP in physiologic responses to PGs remains to be established.

Since prostaglandins (PGs) appear to be important in the pathogenesis of secretory diarrhoea, a radioimmunoassay for determination of PGE2 was applied to purified samples of jejunal fluids aspirated at the ligament of Treitz. Studies on validation of the assay system included quantification of PGE2 following alkali-treatment of the samples, variation of the sample volume, and fractionation of immunoreactive- and tracer PGE2. In addition, the specificity of the assay system was confirmed by gas chromatography--mass spectrometry. In healthy volunteers (n = 22) the PGE2 concentration range was 5--205 pg/ml (99% confidence limits). Alcohol addicts (n = 27) with diarrhoea or steatorrhoea had PGE2 levels within the normal range. Values beyond the 99% upper confidence limit were observed in ten out of seventeen patients with chronic diarrhoea (205--340 pg/ml) and two out of fifteen patients with intermittent diarrhoea (265 and 275 pg/ml) classified as irritable bowel syndrome. In six patients with high PGE2 concentrations indomethacin treatment (25 mg x 4 daily) halved the associated diarrhoea and reduced PGE2 concentrations to normal levels. Subsequently, a double-blind multiple randomized clinical trial was carried out in two single patients. Indomethacin proved to be effective in preventing diarrhoea only in the patient with a raised PGE2 level (P less than 0.005).

Both experimental cholecystitis and luminal distension inhibit fluid absorption and stimulate motor activity in the gall bladder. These functional alterations are mimicked by exogenous prostaglandins (PGs) and inhibited by potent cyclooxygenase inhibitors, but direct evidence of a primary role of endogenous PGs is not available. Therefore, experiments in the cat were carried out in which the effects of lyso-phosphatidylcholine (lysoPC; 0.5-2.0 mmol/l), implantation of cholesterol stones, and raised intraluminal pressure in the gall bladder lumen were assessed. The gall bladder was perfused in vivo at a constant rate by a buffer solution. PGE2 was determined in the effluent by a radioimmunological method validated by gas chromatography-mass spectrometry. PGE2 output was markedly (p less than 0.01) raised (13.9 +/- 2.6 vs 1.1 +/- 0.5 ng/h; n = 10) during lysoPC perfusions and this response was inhibited by 66% (p less than 0.02) after indomethacin administration (2 mg/kg iv). A significant (p less than 0.05) increase in PGE2 output occurred six weeks after implantation of gall stones (3.7 +/- 1.5 ng/h; n = 6) and in response to distension of the normal gall bladder wall (3.6 +/- 1.2 ng/h; n = 6). These findings support the theory that PGs play an important pathophysiologic role in biliary tract disease.

Whole colon perfusion studies and measurements of luminal prostaglandin E2 were carried out in a 41-year-old female with collagenous colitis to investigate pathophysiological mechanisms for the diarrhea. Biopsies of the colorectal mucosa had revealed a continuous 25- to 60-micron subepithelial collagenous layer, but normal junctional complexes and capillaries. When the patient fasted, the diarrhea persisted and fecal electrolytes, as estimated from the concentration of sodium, potassium, and their anions, accounted for all the osmolality (284 mosm/kg) of stool water, the pH of which was above 8.0. The lumen-negative electrical potential difference in the rectum was -64 mV vs -45 +/- 2 mV (mean +/- SEM) in healthy controls. Profuse secretion of fluid and electrolytes occurred during colonic perfusion with saline. Transport of sodium appeared to be passive with flux ratios equal to those predicted for passive sodium movements, while chloride transport against a steep electrical gradient indicated active secretion. Perfusion with an "ileal output"-like solution decreased fluid and electrolyte secretion, suggesting that bicarbonate, in addition to chloride, may be a major determinant of secretion rates. Since immunoreactive prostaglandin E2 levels following in vivo equilibrium dialysis of feces ranged from 555 to 650 pg/ml vs 55 to 235 pg/ml (99% confidence limits) in healthy controls, it is speculated that prostaglandins synthesized locally in response to mucosal hypoxia might be the mediators of anion secretion.

In the presence of indomethacin serosal application of PGEi and PGE2 caused significant inhibition of net isosmotic fluid transport by the gall-bladder with maximum effect (50 % inhibition) at 0.5 ftg PGE/ml. Mucosal application was much less effective. PGF2a was about 100 times less potent than PGE. In the absence of indomethacin the sensitivity to low concentrations of PGEi was about 10 times less than in the presence of this drug (p < 0.001). Maximum effective doses of PGEi depressed the unidirectional Na+-efflux about 35 % and the Na+-influx about 20 %. Transepithelial potential difference and ohmic resistance remained unchanged. It is concluded that PGE inhibits isosmotic fluid transport by an effect mainly on the active component of the transfer process. In the absence of indomethacin endogenous PGE2 (but not PGEi) was released to both serosal and mucosal medium. Net release to mucosal medium was 35–600 pg.h-1.mg dry weight-1; release was higher to the serosal medium. Mucosal concentrations of 0.2–4.5 ng PGEa/ml were independent of the serosal concentration, which did not exceed 0.8 ng/ml under the present conditions. The data suggest that mucosal PGEs-release originates, in part at least, from the epithelial cells. Indomethacin (10 μg/ml) blocked almost completely the in vitro PGE-biosynthesis.

5-Hydroxytryptamine (5-HT) has been claimed to mediate intestinal secretion in morphine withdrawal diarrhea through stimulation of local prostaglandin formation without involving cyclic adenosine monophosphate. Therefore, experiments were performed to study (a) the effects of exogenous 5-HT and the cyclic adenosine monophosphate-dependent secretagogue, vasoactive intestinal polypeptide, on intestinal prostaglandin E2 (PGE2) formation and (b) the involvement of calcium in the secretory response to close intraarterial infusion of 5-HT, PGE2, or vasoactive intestinal polypeptide in tied-off loops of rat jejunum in vivo. 5-Hydroxytryptamine and vasoactive intestinal polypeptide reversed fluid absorption to net secretion (p less than 0.01), but only 5-HT caused an increase in luminal PGE2 output (p less than 0.01). Indomethacin and d,l-verapamil prevented only the secretory effect of 5-HT. Exogenous PGE2 (1.6-160 ng/min) reversed absorption to secretion (p less than 0.01) in a dose-dependent manner, irrespective of whether the rats were pretreated with indomethacin or not. Racemic and l-verapamil, but not d-verapamil, markedly reduced (p less than 0.01) the secretory effect of physiologically low doses of PGE2 (1.6 and 16 ng/min), whereas high doses of PGE2 (160 ng/min), which caused a significant increase in mucosal cyclic adenosine monophosphate (p less than 0.005), were not inhibited by verapamil. These data suggest that PGE2 may be an important intermediate in the transduction mechanism leading to 5-HT-induced intestinal secretion, and that physiologic doses of PGE2 may act by facilitating calcium entry, rather than by increasing intracellular calcium through activation of the adenylate cyclase.

To examine pharmacokinetics and tolerance of long term administration of olsalazine (azodisalicylate), increasing doses of the drug were given for one year to 31 patients with ulcerative colitis (UC) and nine patients with Crohn's colitis (CC), refractory to, or intolerant of sulphasalazine, until sustained remission was obtained or a maximum of 4 g/day was reached. Colonic drug metabolism was studied by equilibrium in vivo dialysis of faeces. Complete azoreduction occurred in most cases. Concentrations of 5-aminosalicylic acid, but not N-acetyl-5-aminosalicylic acid, in faecal dialysates increased dose dependently. Serum concentrations disclosed no cumulation in the long term and olsalazine was well tolerated, although loose stools occurred transiently in some patients with extensive disease: this was associated with a larger proportion of unsplit olsalazine in the faecal dialysates. Patients with ulcerative colitis having a high prostaglandin E2 concentration (greater than ng/ml) determined by equilibrium dialysis of rectum, were less likely to benefit from treatment. Olsalazine is a very effective means of delivery of 5-aminosalicylic acid to the colonic mucosa in active disease. Use of the drug in controlled trials may be considered safe even in prolonged high dosage.

The possible effect of sulfasalazine, 5-aminosalicylic acid, and acetyl-5-aminosalicylic acid on endogenous arachidonic acid release and metabolism was studied in human polymorphonuclear leukocytes (PMNs). A new in vitro assay was used by which [1-14C]arachidonic acid is incorporated by purified peripheral PMNs until steady state was obtained (5 hr). After preincubation with the test drugs prior to activation with calcium ionophore A23187, the released eicosanoids were isolated by extraction and thin-layer chromatography (TLC) and quantitated by autoradiography and laser densitometry. Median drug concentrations needed for 50% inhibition of leukotriene B4 and 5-hydroxyeicosatetraenoic acid (5-HETE) release was 4-5 mM (range 1-9 mM) for both sulfasalazine and 5-aminosalicylic acid. The acetylated derivative of 5-aminosalicylic acid was ineffective. The present data suggest that inhibition of arachidonic acid lipoxygenation may be an essential action of sulfasalazine and its active metabolite, 5-aminosalicylic acid. Interference with lipoxygenase enzymes, rather than a steroid-like inhibition of arachidonic acid release from intracellular phospholipids, seems to be the mode of action.

The mechanisms responsible for maintaining the integrity of the gastroduodenal mucosa have been explored intensively in recent years. Prostaglandins seem to play a central role in mucosal defence. Important mechanisms by which prostaglandins may produce cytoprotection include regulation of the thickness and the composition of the mucus layer at the epithelial surface; modulation of active bicarbonate secretion by the surface epithelial cells; hydrophobicity of the surface epithelium; rapid cell proliferation and differentiation after mucosal damage; maintenance of interstitial bicarbonate; and the integrity of the microcirculation--in addition to synthesis of mucosal sulphhydryl groups. A defect mucosal defence is considered the most important pathogenetic factor in the majority of patients with peptic ulcer disease, but it is still unclear whether this is due to a deficiency in endogenous prostaglandins. Important risk factors for developing peptic ulcer disease, such as nonsteroidal antiinflammatory drugs and smoking, depress the formation of endogenous prostaglandins. The question of whether the use of direct cytoprotection may be relevant in ulcer therapy has yet not been solved and the rationale for substitution with prostaglandin analogues is to date empirical.

To establish whether concentrations of eicosanoids determined by equilibrium in vivo dialysis of faeces and equilibrium in vivo dialysis of rectum might predict a relapse in ulcerative colitis, 23 patients with completely inactive disease, maintained on sulphasalazine, stopped treatment and entered a prospective study. Concentrations of prostaglandin E2 were determined by radioimmunoassay on purified faecal and rectal dialysates at entry, at two weeks, and at two, six, and 12 months. If the above concentrations exceeded control concentrations (0.5 ng/ml and 1.0 ng/ml in faecal and rectal fluid, respectively) at any study day, the patient was allocated at random to double blind treatment with sulphasalazine 2 g/day, or placebo for six months. A relapse, defined as recurrence of symptoms accompanied by endoscopic inflammation occurred in none of six and in four of five patients allocated to sulphasalazine and placebo, respectively (p less than 0.05). In no case a normal rectal prostaglandin E2 concentration was associated with a relapse in the short term, but only two of 12 patients observed passively remained in remission. In retrospect, leukotriene B4 was a less sensitive predictor of relapse than prostaglandin E2. We conclude that raised concentrations of prostaglandin E2 in rectal dialysis fluid identify patients with a substantial risk of relapse.

It has been proposed that anti-inflammatory actions of corticosteroids rely on promotion of a natural peptide phospholipase A2 inhibitor, lipocortin, but in vivo effects on arachidonic acid metabolism have not been shown. Equilibrium dialysis of the rectum in patients with ulcerative colitis was used to determine whether cyclooxygenase and lipoxygenase products released from the inflamed rectal mucosa could be differentially inhibited by systemic treatment with prednisolone and indomethacin, respectively. In 10 patients with severe disease luminal concentrations of prostaglandin E2, prostaglandin F2 alpha, and leucotriene B4 were markedly raised (p less than 0.05) on comparison with 10 healthy controls, and they decreased significantly (p less than 0.05) within 72 hours after administration of prednisolone 1.5 mg/kg/day orally. In contrast prostaglandin, but not leucotriene B4 concentrations decreased (p less than 0.05) within 72 hours after administration of indomethacin 150 mg/day in another 10 patients with distal disease. These prompt reductions in concentrations of arachidonic acid metabolites more likely are caused by direct drug actions, rather than being secondary to decreased tissue damage. The data accord with the theory explaining anti-inflammatory effects of corticosteroids through lipocortin activity and support the belief that leucotrienes are more important than prostaglandins as mediators of inflammation in ulcerative colitis.

To investigate the causal relationship, if any, between gastric PG formation and gastric acid output, the release of PGE2 into gastric juice has been studied in eight beagle dogs with a gastric fistula, using sustained half-maximal stimulation by bethanechol and pentagastrin, and in eight duodenal ulcer patients, using the combined sham feeding/pentagastrin test. Immunoreactive PGE2 was determined by a method validated by gas chromatography-mass spectrometry and PGE2 values were normalized by expressing them as ng PGE2 released per meq H+ secreted. In the dogs "steady state" PGE2 output (0.4-10 ng/meq H+) was interrupted during continuous i.v. pentagastrin infusion by symmetrical peaks (50-60 minutes of duration) with a maximum of 24 +/- 3.1 ng/meq H+ (mean +/- SEM). During bethanechol stimulation the rhythmic variations were smaller, but the median values for the periods 30 to 180 or 240 minutes significantly (p less than 0.01) higher (3.9-46 ng/meq H+) than in pentagastrin experiments (0.8-20 ng/meq H+). In humans the peak PGE2 output during sham feeding (3.4-41 ng/meq H+) was significantly (p less than 0.02) larger than following bolus stimulation (6/micrograms/kg) by pentagastrin (2.2-18 ng/Meq H+). The findings are consistent with the hypothesis that activation of muscarinic receptors represents the physiologic mechanism by which gastric release of PGs is regulated. Cyclic variations in gastric PG formation appear to occur in response to vagal stimulation since the peaks in PGE2 output were preceded by increased myoelectrical activity (i.e. mean contractile index).

To determine the influence of inflammation and topical treatment with 5-aminosalicylic acid or prednisolone on arachidonic acid metabolism in vivo, we carried out a double-blind controlled study on the release of prostaglandin E2 and leukotriene B4 to the rectal lumen in 24 consecutive patients with proven distally located ulcerative colitis. Before and at days 15 and 29 a dialysis bag was placed in the emptied rectum for 4 h prior to assessing clinical, endoscopic, and histologic disease activity. A single enema was given daily at bedtime (1 g 5-aminosalicylic acid or 25 mg prednisolone) until complete remission or for a maximum of 4 wk. Clinical and endoscopic remission was obtained in 16 (7 on 5-aminosalicylic acid) and 11 (3 on 5-aminosalicylic acid) patients, respectively. Luminal concentrations of prostaglandin E2 and leukotriene B4 were positively correlated to disease activity and significantly decreased among the prednisolone-treated patients. In both treatment groups a decrease toward normal levels occurred in patients responding to therapy. In retrospect, the pretreatment prostaglandin E2 and leukotriene B4 levels were significantly higher in patients not responding to therapy than in those improving during treatment. In conclusion, luminal prostaglandin E2 and leukotriene B4 levels may prove more useful predictors of the outcome of treatment in relapsing ulcerative colitis than clinical indices of disease activity.

To determine whether supplementation with the physiological radical scavenger, vitamin E, would modulate arachidonate metabolism in human inflammation, we performed equilibrium dialysis of rectum in eight patients with active ulcerative colitis confined to the rectum. The patients, all off drug treatment, were supplemented with 1920 IU/day of alpha-tocopherol and had rectal dialysis done at entry and after three and 14 days. Luminal concentrations of prostaglandin E2 (PGE2) and leukotriene B4 (LTB4), determined by radioimmunoassay in purified dialysates, were significantly raised compared to healthy controls. Supplements caused no change in these levels either at day 4 or 15, although serum-tocopherol showed a 3-fold increase. Also disease activity was unaffected. This failure of vitamin E supplementation to suppress the mucosal release of PGE2 and LTB4 in active inflammation does not encourage controlled trials on the effect of oral vitamin E in ulcerative colitis.

Biochemical and clinical evidence is presented to indicate that prostaglandin (PG)E2 is the mediator of fluid and electrolyte secretion by villous adenomas of the rectum. A 64-yr-old man with a 2-mo history of mucous diarrhea had, on admission, prerenal uremia, severe hyponatremia, and hypokalemia. At sigmoidoscopy an 11 X 11-cm villous adenoma of the rectum was revealed. The rectal fluid discharge was 1800-1825 ml/day, with sodium and potassium concentrations of 150 and 12 mEq/L, respectively. Immunoreactive PGE2 levels in the rectal effluents were high (viz. 1160-1250 pg/ml vs. 200-395 pg/ml) compared with those in stool water from patients with infectious diarrhea. The concentration of vasoactive intestinal polypeptide (VIP) in the tumor was lower (viz. 10.5 pmol/g vs. 100-700 pmol/g) than in normal colonic mucosa. Indomethacin treatment (24 mg X 4 daily) reduced the rectal PGE2 excretion from 2.2 to 0.3 microgram/day and caused a decrease in the rectal fluid loss of 850 ml/day associated with a similar reduction in rectal sodium excretion. Discontinuing medication, a rise in the rectal excretions of PGE2, fluid, and sodium was observed. In conclusion, PGE2 formation in the villous adenoma appears to be the cause of fluid secretion by the abnormal tumor epithelium. The use of PG synthetase inhibitors may facilitate the preoperative correction of severe fluid-electrolyte deficits in patients with large villous adenomas of the rectum.

In order to determine the arterio-venous difference in circulating prostaglandin levels the isotope derivative technique was applied to rat plasma for measurements of prostaglandin E2 (PGE2). No arterio-venous difference was observed if the blood was collected without precautions to avoid in vitro prostaglandin production in the sampling tube. In contrast, inhibition of the in vitro prostaglandin release by the infusion of indomethacin into the catheter from which the blood was drawn, showed PGE2 levels in the right atrium of 60 +/- 20 pg/ml (mean +/-SD; N = 8), and peripheral levels insignificantly different from zero. A significant difference in PGE2 levels of right atrial plasma from fed and fasted rats was observed without the use of in vitro indomethacin in blockade (210 +/- 70 pg/ml; N=4, and 330 +/- 35 pg/ml; N = 4, respectively). This difference could not be reproduced if indomethacin was infused into the catheter (60 +/- 20 pg/ml; N = 8 and 90 +/- 35 pg/ml; N = 5, for fed and fasted rats, respectively). Measurements by radio-gas-liquid-chromatography of the arachidonic acid plasma level showed values of 6.8 +/- 1.6 micrometers (N = 7) and 12.0 +/- 3.4 micrometers (N = 7) for fed and fasted rats, respectively. It is suggested that the higher level of PGE2 (without indomethacin) in fasted rats reflects that of arachidonic acid. The present available methods for the determination of primary prostaglandins and prostaglandin metabolites are discussed with respect to their value not only in physiological studies on fluid and electrolyte transport in the gut, but also for clinical use.