Inhibitory effect of hypochlorous acid on lower esophageal sphincter tone relaxation by vasoactive intestinal peptide

Under physiological conditions, hypochlorous acid (HOCl) is the major product of myeloperoxidase, a ferric heme enzyme released in inflammatory diseases. In the present study, we investigated the effect of HOCl compared to hydrogen peroxide (H2O2) on the vasoactive intestinal polypeptide (VIP)-induced relaxation of feline lower esophageal sphincter (LES) strips. Isometric tension on LES strips was measured using a force transducer. VIP induced the relaxation of basal LES tone in a concentration-dependent manner. Pretreatment with HOCl (10(-4) M) significantly reduced the VIP-induced relaxation at smaller concentrations than H2O2 (10(-3) M). VIP-induced relaxation is mediated via the Gi/o protein, since pretreatment with Pertussis Toxin (PTX) showed an inhibitory effect on the relaxation. HOCl showed an additional inhibitory effect on the reduced relaxation by PTX, indicating that HOCl might affect another G protein as well as Gi/o. However, HOCl did not affect SNP-, SIN-1-, and 8-br-cGMP-induced relaxation. Nor did HOCl modify the relaxation induced by either forskolin or db-cAMP in LES muscle strips. These results suggest that during short-term treatment, HOCl may damage the upstream events including G protein level, and result in alteration of LES tone in the feline esophagus, similar to the inhibitory effects of H2O2.

Lactulose feeding lowers cecal densities of clostridia in piglets

BACKGROUND

In order to understand the consequences of persistent enteral feeding in patients with carbohydrate malabsorption, we fed piglets lactulose in sufficient dosage to produce osmotic diarrhea or inulin, using a conventional dose, to determine if this prebiotic can modulate the effects of lactulose. Feeding lactulose increases cecal luminal synthesis of butyrate, with inulin having an intermediate effect. Because clostridia may be a major source of colonic butyrate production, we hypothesized that feeding piglets lactulose or inulin would increase cecal densities of clostridia.

METHODS

Piglets were assigned to 3 formula study groups for 6 days: (1) control, fed only sow milk replacer (n = 12); (2) inulin, inulin supplement (3 g/L; n = 11); and (3) lactulose, lactulose supplement (66.7 g/L; n = 6). Cecal fluid for bacteriological studies was sampled intraoperatively.

RESULTS

The wet/dry ratio of the cecal contents (mean +/- SEM) was 8.2 +/- 0.5, 6.2 +/- 0.5, and 18.8 +/- 5.5, respectively, in the control, inulin, and lactulose groups (p = .049, Kruskal-Wallis). There were no differences among the diet groups for cecal densities (10(6) colony-forming units [CFU]/g dry wt cecal contents) of total anaerobes, total aerobes, bifidobacteria, or lactobacilli. Densities of clostridia were markedly reduced in the lactulose group (1.14 +/- 0.41) vs the control (18.39 +/- 4.44; p = .001) or inulin groups (8.87 +/- 2.20; p = .04).

CONCLUSIONS

In piglets, feeding lactulose at a dose known to cause diarrhea reduces cecal densities of clostridia.

Glucose-dependent insulinotropic polypeptide modulates adipocyte lipolysis and reesterification

OBJECTIVE

Glucose-dependent insulinotropic polypeptide (GIP) is an incretin released from intestinal K-cells during the postprandial period. Previous studies have suggested that GIP may play an etiologic role in obesity; thus, the GIP receptor may represent a target for anti-obesity drugs. The present studies were conducted to elucidate mechanisms by which GIP might promote obesity by examining the effect of GIP on both glycerol release (indicative of lipolysis) and free fatty acid (FFA) release (indicative of both lipolysis and reesterification), as well as the ability of a GIP-specific receptor antagonist (ANTGIP) to attenuate these effects.

RESEARCH METHODS AND PROCEDURES

Isolated rat adipocytes were perifused on a column with 10 nM GIP alone or in combination with 10 microU/mL insulin, 1 microM isoproterenol, or 1 microM ANTGIP. Samples were collected every minute and assayed for FFA, glycerol, and lactate.

RESULTS

GIP significantly increased FFA reesterification (decreased FFA release by 25%), stimulated lipolysis (increased glycerol release by 22%), and attenuated the lipolytic response to isoproterenol by 43%. These properties were similar to those of insulin in vitro, suggesting that GIP possesses insulin-like lipogenic effects on adipocytes. Finally, ANTGIP reversed the effects of GIP on both basal and stimulated adipocyte metabolism.

DISCUSSION

These studies provide further evidence for an important physiological role for GIP in lipid homeostasis and possibly in the pathogenesis of obesity. They also suggest that the GIP receptor may represent an excellent target for the prevention and treatment of obesity and obesity-related type 2 diabetes.

Effect of pancreastatin on cerulein-stimulated pancreatic blood flow and exocrine secretion in anaesthetized rats

BACKGROUND

Pancreastatin (PST) is an inhibitor of pancreatic exocrine secretion in vivo but not in vitro, which suggests that the inhibitory effect of PST is indirect, that is, not mediated by a specific receptor on pancreatic acinar cells. In this study, we investigated the effects of PST on pancreatic exocrine secretion and local pancreatic blood flow in anaesthetized rats to elucidate the participation of PST in indirect regulation of pancreatic exocrine function through blood supply.

METHODS

Pancreastatin (100, 200 or 500 pmol/kg per h) was administered intravenously under background infusion of cerulein (0.5 microg/kg per h), a cholecystokinin analogue. Pancreatic exocrine secretion was monitored by volume and protein output of the pancreatic juice and local pancreatic blood flow was measured by the hydrogen gas clearance method.

RESULTS

Pancreastatin significantly reduced cerulein-induced local pancreatic blood flow in a dose-dependent manner. Pancreatic exocrine secretion was also reduced significantly by PST dose-dependently. Pancreastatin did not change systemic blood pressure. These results suggested that the reduction of pancreatic blood flow is associated with the reduction of pancreatic exocrine secretion.

CONCLUSIONS

We conclude that the mechanism of PST-induced inhibition of pancreatic exocrine secretion is, at least, partly mediated by the reduction of local pancreatic blood flow through blockade, caused by the action of cerulein on pancreatic blood flow.

Hypotensive mechanism of [Leu13]motilin in dogs in vivo and in vitro

The effects of [Leu13]motilin were examined in vivo after its intravenous administration into anesthetized dogs and in vitro with isolated preparations of canine mesenteric artery. [Leu13]Motilin (0.1-10 nmol x kg(-1), i.v.) induced both strong and clustered phasic contractions in the gastric antrum and duodenum. At doses of over 1 nmol x kg(-1), [Leu13]motilin also produced transient decreases in arterial blood pressure, left ventricular pressure, maximum rate of rise of left ventricular pressure, and total peripheral resistance, and an increase in aortic blood flow and heart rate. A selective motilin antagonist, GM-109 (Phe-cyclo[Lys-Tyr(3-tBu)-betaAla] trifluoroacetate), completely abolished the gastric antrum and duodenal motor responses induced by [Leu13]motilin. In contrast, hypotension induced by [Leu13]motilin (1 nmol x kg(-1)) was unchanged in the presence of GM-109. In isolated mesenteric artery preparations precontracted with U-46619 (10(-7) M), [Leu13]motilin (10(-8)-10(-5) M) induced an endothelium-dependent relaxation, and this was inhibited by a pretreatment with N(omega)-nitro-L-arginine, a competitive inhibitor of NO synthase (10(-4) M). A high dose (10(-4) M) of GM-109 slightly decreased [Leu13]motilin-induced relaxation, and shifted the concentration-response curve of [Leu13]motilin to the right. However, the pA2 value (4.09) of GM-109 for [Leu13]motilin in the present study was conspicuously lower than that previously demonstrated in the rabbit duodenum (7.37). These results suggest that [Leu13]motilin induces hypotension via the endothelial NO-dependent relaxation mechanism and not through the receptor type that causes upper gastrointestinal contractions.

Moderation of lactulose-induced diarrhea by psyllium: effects on motility and fermentation

Psyllium has been reported to inhibit lactulose-induced colonic mass movements and to benefit patients with irritable bowel syndrome, improving both constipation and diarrhea. Our aim was to define how psyllium modified the whole-gut transit of a radiolabeled lactulose-containing test meal by using gamma scintigraphy. Eight subjects participated in a randomized crossover study comparing gastric emptying and small bowel and colonic transit after consumption of 20 mL lactulose three times daily with or without 3.5 g psyllium three times daily. Psyllium significantly delayed gastric emptying: the time to 50% emptying increased from a control value of 69 +/- 9 to 87 +/- 11 min (mean +/- SEM; P < 0.05, n = 8). Small bowel transit was unaltered. However, progression through the colon was delayed with an increase in the percentage of the dose at 24 h in the ascending (control group: 2 +/- 3%, psyllium group: 11 +/- 8%; P < 0.02) and transverse colon (control group: 5 +/- 12%, psyllium group: 21 +/- 14%) with correspondingly less in the descending colon. Although the time for 50% of the isotope to reach the colon was not significantly different with psyllium, psyllium significantly delayed the rise in breath-hydrogen concentrations, which reached 50% of their peak at 217 +/- 34 min compared with control values of 155 +/- 27 min (P < 0.05). Psyllium delays gastric emptying, probably by increasing meal viscosity, and reduces the acceleration of colon transit, possibly by delaying the production of gaseous fermentation products.

Effect of peripherally and centrally administered calcitonin on gallbladder emptying in dogs

The effect of calcitonin on meal-stimulated gallbladder emptying (GBE) was examined after intravenous (i.v.) and intracerebroventricular (i.c.v.) administration in six mongrel dogs. The gallbladder contraction was surveyed by means of real-time ultrasonography in conscious dogs. Calcitonin given i.v. elicited an immediate and strong inhibition of postprandial GBE-the integrated 0- to 120-min gallbladder response was 118.1 +/- 8.0%.h after placebo, whereas it was 91.8 +/- 2.1%.h, 59.4 +/- 17.9%.h (P < 0.001), and 14.2 +/- 20.5%.h (P < 0.001) after 3.6, 18.0, and 90.0 pmol.kg-1 calcitonin, respectively. After i.c.v. administration (1.8 and 18.0 pmol.kg-1), only the higher calcitonin dose exerted a moderate inhibitory effect on postprandial GBE. The calcitonin doses required to evoke a 50% inhibition of meal-stimulated GBE were 15- to 10-fold lower after i.v. than i.c.v. application. Peripherally given calcitonin brought about a dose-dependent increase in the interdigestive gallbladder volume-the linear regression of the relative gallbladder volume versus calcitonin dose was y = 11.60 [ln(dose + 1)] + 97.02 (r = 0.864, P < 0.001). Intravenous application of calcitonin did not affect caerulein-induced GBE. The results obtained imply that: (i) calcitonin exerts an inhibitory influence on meal-induced GBE and that this effect is more pronounced after i.v. than after i.c.v. administration, and (ii) peripherally given calcitonin does not inhibit caerulein-induced gallbladder contraction in the dog.

Effect of the oral administration of sepimostat mesilate on cerulein induced acute pancreatitis in rats

The effect of a potent protease inhibitor, sepimostat mesilate (CAS 103926-82-5, FUT-187), on acute interstitial edematous pancreatitis induced by a supramaximal dose of cerulein, a cholecystokinin (CCK) analogue, was evaluated. The serum amylase activity increased 18-fold over normal control after the infusion of cerulein at 5 micrograms/kg/h for 6 h. The serum lipase activity showed a 235-fold increase. An elevated pancreatic water content, pancreatic interstitial edema, inflammatory infiltration and vacuolization of the acinar cells were found. Redistribution of cathepsin B shifted from the lysosomal pellet fraction to the zymogen granule pellet fraction was noted in the early stages. All these parameters of pancreatitis mentioned above were inhibited by FUT-187 pretreatment at doses of 30 to 300 mg/kg. These observations suggest that FUT-187 inhibits the redistribution of cathepsin B shift from the lysosomal fraction to the zymogen fraction in cerulein-induced acute pancreatitis and improves the parameters of acute pancreatitis.