Prophylaxis with ketotifen in rats with portal hypertension: involvement of mast cell and eicosanoids

BACKGROUND

Since we have previously shown an increase of mast cells in the small bowel and in the mesenteric lymph nodes in the rats with prehepatic portal hypertension, it can be hypothesized that this essential inflammatory cell would be involved in the pathogeny of the splanchnic changes related to portal hypertension.

METHODS

To verify this hypothesis, we first studied mast cell infiltration in the ileum and in the mesenteric lymph nodes in sham-operated male Wistar rats (n=12) and in short-term prehepatic portal hypertensive rats (n=12), and the serum levels of rat mast cell protease II (RMCP-II) by ELISA. In a second set of experiments ketotifen, a mast cell stabilizer drug, was administered to sham-operated (n=10) and portal hypertensive (n=12) rats 24 hours before the intervention and prostanoids (PGE2, PGI2, TXB2) and leukotrienes (LTC4, LTB4) were assayed by RIA, mast cell infiltration in the ileum and in the mesenteric lymph nodes and the serum levels of RMCP-II were also studied, to show its effectiveness to prevent the mesenteric alterations produced by the inflammatory mediators released by the mast cell.

RESULTS

Forty-eight hours after the intervention RMCP-II (P<0.05), PGE2 (P<0.001) and LTC4 serum levels decreased and mast cell number and RMCP-II levels increased in mesenteric lymph nodes in portal hypertensive rats. Prophylactic administration of ketotifen reduced portal pressure (P<0.001), serum levels of PGE2 (P<0.001) and RMCP-II (P<0.001) in mesenteric lymph nodes.

CONCLUSIONS

In acute portal hypertension in the rat, the mast cell translocation from intestinal mucosa to mesenteric lymph nodes, where they are activated and degranulates, would represent a defence mechanism to avoid the activation of an acute and massive inflammatory response in this location. Prophylactic administration of ketotifen is able to reduce the splanchnic inflammatory changes related to acute portal hypertension in the rat.

Hypersensitivity to ovalbumin induces chronic intestinal dysmotility and increases the number of intestinal mast cells

Undiagnosed food allergies have been proposed as possible causes of promoting and perpetuating irritable bowel syndrome . Our aim was to find out if sensitization could induce chronic functional motor disturbances in the intestine and the mechanisms implicated. Rats were sensitized to ovalbumin (OVA) following three hypersensitivity induction protocols, two parenteral and one oral. Rat mast cell protease II (RMCP II) release in response to OVA challenge and immunoglobulin E (IgE) concentration were measured in serum. At least 1 week after challenge, small intestinal motility was evaluated using strain gauges. Intestinal tissue samples from orally sensitized rats were checked for in vitro stimulation with OVA. Mucosal mast cells were counted from duodenum sections. All sensitized rats showed intestinal hypermotility. Only rats sensitized by parenteral procedure showed an increase in RMCP II after OVA challenge in serum. IgEs increased only in the Bordetella pertussis sensitized group. Small intestine sections from orally sensitized rats released more RMCP II than sections from control rats. All sensitized rats showed an increase in the number of mucosal mast cells in duodenum. In conclusion, hypersensitivity to food proteins induces chronic motor alteration that persists long after antigen challenge and an excited/activated state of sensitized mucosal mast cells.

Interspecific variation of metal concentrations in three bivalve mollusks from Galicia

There has been growing concern about the inflow of metals to the coastal areas because they can be toxic to aquatic and human life. Some studies have demonstrated the existence of species-specific differences in the metal concentrations of mollusks. We compared metal concentrations between Mytilus galloprovincialis, used as a water quality indicator, and two other bivalve species collected for human consumption (Venerupis pullastra and Cerastoderma edule) in different locations on the Galician coast (northwest Spain). M. galloprovincialis was found to be the best zinc and lead accumulator, whereas silver and arsenic were preferentially accumulated by V. pullastra and chromium and nickel by C. edule. Bivalve concentrations of mercury, cadmium, chromium, arsenic, silver, and zinc appeared to be linearly related to environmental concentrations, but this was not the case with copper, nickel, and lead in some species, which indicated that there is a nonlinear accumulation of these metals or an influence of the environmental conditions on species accumulation. The relationship between metal concentration in mussels and in the two other species varied with the metal and the species. In some cases the correlation was high, making it possible to use mussels as bioindicators for the other species. In other cases the correlation was moderate or low, therefore rendering mussels of little or no use in predicting the metal concentrations in the two other species.

Determination of vanadium in mussels by electrothermal atomic absorption spectrometry without chemical modifiers

A method was developed for the quantitative determination of total vanadium concentration in mussels via electrothermal atomic absorption spectrometry (ETAAS). After the microwave digestion of the samples, a program using temperatures of 1600 degrees C and 2600 degrees C for ashing and atomization respectively, without any matrix modifiers, allowed us to obtain results that were satisfactory since they agreed closely with certified reference material values. The detection limit was 0.03 mg kg(-1) (dry weight), indicating that the method is suitable for the analysis of mussel samples. This determination was compared with matrix modifiers that have been reported previously. The method was applied to various cultivated and wild mussels from the Galician coast, yielding levels below 1 mg kg(-1) (wet weight).

The effect of size on trace metal levels in raft cultivated mussels (Mytilus galloprovincialis)

Mussels are farmed in the coastal inlets of Galicia by means of floating raft culture. The growth of these bivalves is due to their great capacity to filter the water column, which unfortunately, also exposes them to dangerous contaminants, including heavy metals. Thus, it is imperative that mussels be monitored for metals. Size has sometimes been shown to be an important variable, but contradictory results have been found. In order to monitor metals in raft mussels, it is necessary to compile information regarding the number of size classes according to shell length, which must be taken into account to obtain a representative sampling, as well as the number of sample replicates that must be included. Also, to be considered is the cost incurred by carrying out the collection, preparation and analysis per sample. The purpose of this study is to provide information about the effect of size, indicated by shell length on the metal content of raft mussels. The ability of 10 mussel-pooled samples to discriminate real differences in metal concentration was also studied. In general, a positive relationship between metal content and shell length was observed; a similar relation was found between the weight of soft tissues and shell length. As expected from the similarity encountered between relationships of metal content and dry weight-length, the concentrations of the different metals in the soft tissues would not seem to depend on the shell length. Metal concentrations, in this study, were found to be approximately 45 ppm of Hg, 0.5 ppm of Cd, 0.7 ppm of Pb, 0.5 ppm of Cr, 0.6 ppm of Ni, 8 ppm of As, 5 ppm of Cu and 122 ppm of Zn; on a dry weight basis. No significant differences between metal concentrations at different shell lengths were detected. Another important observation was the high variability observed within one size, indicating poor homogeneity in subgroups of similar size, which must be minimized if the number of samples is not enhanced as indicated by power and size analysis.

Somatostatin inhibits intestinal mucosal mast cell degranulation in normal conditions and during mast cell hyperplasia

Several studies demonstrate that intestinal mucosal mast cells (IMMC) are modulated by nervous reflexes as well as by intraluminal content. We recently demonstrated that peptones, such as ovalbumin hydrolysate (OVH), induce the release of rat mast cell protease II (RMCP II), indicating IMMC degranulation. The response is due to complex neuroendocrine reflexes. Somatostatin (SS) and its analogues have been used as potential treatments for inflammation in other body systems with contradictory results. The aim of this study was to evaluate if somatostatin could contribute to the reduction of intestinal mucosal mast cell degranulation. Anesthetized rats were prepared for duodenal perfusion and mast cell activation was measured by analysis of RMCP II concentration in the duodenal perfusate. Somatostatin significantly decreased RMCP II concentration in both nonstimulated conditions and after ovalbumin hydrolysate perfusion. However, when somatostatin was given previously to OVH, the peptone still induced a slight increase of RMCP II. Similar effects were observed in animals previously treated with capsaicin. These protocols were repeated in animals infected with Trichinella spiralis, which induces mucosal mast cell hyperplasia. In these cases, somatostatin blocked the effect of OVH, thus, preventing an increase in RMCP II concentration. Fresh frozen tissue sections from the duodenum were processed in an attempt to demonstrate the presence of SS receptors in mast cells using immunofluorescence and Fluo-peptide labeling techniques. Confocal images from duodenum specimens demonstrate the existence of SS receptors in positive cells for RMCP II. Taken together, these results indicate that somatostatin diminishes mast cell activity and in consequence could prevent the intestinal responses to mast cell hyperplasia.

Neuroendocrine control of intestinal mucosal mast cells under physiological conditions

Mast cells are involved in the pathogenesis of both allergies to food and inflammatory bowel disorders. In addition, there are several lines of evidence suggesting that mucosal mast cells also respond to intraluminal stimuli. Our aim was to identify neuroendocrine stimuli that could modify mucosal mast cell activity in the rat. Anaesthetized rats were prepared for duodenal perfusion and mast cell activation was measured by analysis of RMCP II concentration in the duodenal perfusate. Either buffered saline solution or a 5% ovalbumin hydrolysate (OVH) solution was infused into the duodenum. Subdiaphragmatic vagotomy or afferent ablation by intraluminal treatment with capsaicin diminished RMCP II concentration in basal conditions and significantly reduced the response to OVH, which in control animals induced a three-fold increase of the protease. The noradrenergic blockers phentholamine and propranolol significantly diminished RMCP II concentration in basal conditions and completely blocked the response to OVH. Intravenous infusion of cholecystokinin-related peptides also induced a response of mast cells. However, the response was different depending on the peptide. CCK-8 induced a slight increase of RMCP II, whereas both CCK-33 and gastrin induced a significant decrease in mast cell activity. These results show that intraluminal content modulates mucosal mast cell activity by complex mechanisms involving both nervous and endocrine pathway.