Hiroshi Shiozaki

Changes in intestinal absorption of nutrients and brush border glycoproteins after total parenteral nutrition in rats.

The effect of total parenteral nutrition on nutrients absorption and glycoprotein changes of brush border membrane was examined in rat small intestine. In total parenteral nutrition rats, a marked decrease in activity of brush border enzymes was observed mainly in the proximal and middle segments of the intestine. Galactose perfusion of jejunal segment showed that hexose absorption was significantly inhibited, while intestinal absorption of glycine or dipeptide, glycylglycine was not significantly affected by total parenteral nutrition treatment. When brush border membrane glycoprotein profile was examined by [3H]-glucosamine or [3H]-fucose incorporation into jejunal loops, significant changes were observed in the glycoprotein pattern of brush border membrane especially in the high molecular weight range over 120 kDa after total parenteral nutrition treatment, suggesting strong dependency of glycoprotein synthesis on luminal substances. Molecular weight of sucrase isomaltase in brush border membrane detected by specific antibody showed no significant difference, however, in total parenteral nutrition and control rats. Also, molecular weight of specific sodium glucose cotransporter of intestinal brush border membrane detected by selective photoaffinity labelling was not altered in total parenteral nutrition rats. It may be that prolonged absence of oral food intake may produce significant biochemical changes in brush border membrane glycoprotein and absorptive capacity of small intestine, but these changes were not observed in all brush border membrane glycoproteins.

Role of platelet activating factor on the fibrinolytic activation in the pathogenesis of gastric mucosal damage induced by endothelin-1.

We have examined the hypothesis that the release of tissue type plasminogen activator may play a prominent role in endothelin induced gastric mucosal injury. We determined tissue type plasminogen activator activity in the regional blood sample and the concentration of platelet activating factor in the gastric mucosa after the administration of endothelin-1 in a range of 50-500 pmol/kg into the left gastric artery of male Wistar rats. Endothelin-1 increased the tissue type plasminogen activator release and platelet activating factor formation, and induced subsequent gastric mucosal haemorrhagic change in a dose dependent manner. In addition CV-6209, a selective platelet activating factor blocker, attenuated the activation of regional tissue type plasminogen activator and the development of mucosal damage induced by endothelin-1. The results of this study showed that tissue type plasminogen activator activation may play an important role in the pathogenesis of endothelin induced mucosal injury of rat stomach, and suggest that the platelet activating factor may be involved in the process of regional fibrinolytic activation induced by endothelin-1.

Role of Erythrocytes as a Reservoir for Ribavirin and Relationship with Adverse Reactions in the Early Phase of Interferon Combination Therapy for Chronic Hepatitis C Virus Infections

ABSTRACT We investigated the relationship between serum ribavirin concentrations and clearance, as well as therapeutic efficacy and adverse reactions, in 97 Japanese patients with chronic hepatitis C virus infections treated with a 6-month course of high-dose alpha2b interferon (6 million units/day) plus ribavirin (600 to 800 mg/day) combination therapy. This randomized trial showed that the saturation of ribavirin uptake after taking ribavirin capsules does not occur within a dose range of 600 to 800 mg/day, which is a standard dosage used clinically in Japan. Serum ribavirin concentrations and clearance did not correlate with sustained virological response rates. Fourteen patients discontinued therapy because of adverse reactions, and sustained virological response rates were significantly reduced by discontinuation of therapy, while dose reduction of ribavirin did not alter the therapeutic effects. Ribavirin concentrations after 1 week and ribavirin clearance were significantly correlated with discontinuation of ribavirin; however, a multiple-regression analysis revealed that only hemoglobin concentration, but not ribavirin clearance, was a significant factor for discontinuation of therapy (odds ratio, 0.514; 95% confidence interval, 0.311 to 0.85; P = 0.0095). It appears that peripheral erythrocytes may act as a reservoir for ribavirin and regulate serum ribavirin levels in the very early phase of treatment.

Alteration of Mucosal Immunity After Long-term Ingestion of an Elemental Diet in Rats

The effects of an elemental diet on lymphocyte transport in intestinal lymph and immune responses of gut-associated lymphoid tissue were investigated in rats. The control animals were fed a conventional diet. After 4 week of feeding, the total calorie intake and body weight gain showed no differences between the two groups. The number and total area of Peyers patches and the ratio of height of villi to height of crypt showed no significant differences between the two groups. The rate of lymph flow in intestinal lymphatics showed no significant change in treated animals compared with the control rats. However, an elemental diet induced a significant decrease in lymphocyte flux in intestinal lymphatics compared with that in control rats. Lymphocyte subsets in intestinal lymph revealed a significant decrease in CD3-positive cells, especially CD4-positive cells in the elemental diet-treated group. A significant decrease in the number of immunoglobulin A-containing cells and a decreased CD4/CD8 ratio in T-cell subsets were observed in the lamina propria of ileal mucosa in the elemental diet-treated group by morphometric analysis in the immunohistochemical study. Specific antibody-secreting cells in intestinal lymph were also investigated after rats were intraduodenally primed with cholera toxin and challenged with the same toxin after an interval of 2 weeks. No significant difference was seen between the two groups in any of the numbers of anti-cholera toxin immunoglobulin-secreting cells in any immunoglobulin A, immunoglobulin G, or immunoglobulin M class as determined by the enzyme-linked immunospot assay.(ABSTRACT TRUNCATED AT 250 WORDS)

Conjugated bile salts regulate turnover of rat intestinal brush border membrane hydrolases

The mechanisms whereby the conjugated bile salts regulate the activities of the brush border membrane hydrolases and its physiological significance were investigated in rat small intestine, and comparisons were made with the action of pancreatic protease. Rat brush border membrane proteins were metabolically labeled with [35S]methionine, and isolated brush border membrane was incubated with taurocholate or pancreatic elastase. The activity of solubilized hydrolases was assayed and the molecular forms of the hydrolases were examined by SDS-PAGE. The activity and protein bands of alkaline phosphatase and sucrase-isomaltase were solubilized by taurocholate, while alkaline phosphatase was not solubilized by elastase. Solubilized sucrase-isomaltase molecules were proteolytically degraded by elastase, whereas the intact molecule of sucrase-isomaltase was solubilized by taurocholate. Next the physiological role of bile salts in brush border membrane hydrolase turnover were investigated using metabolic labeling of brush border membrane hydrolase and immunoprecipitation in biliary diversion rats. After three days of biliary diversion, a significant increase in alkaline phosphatase activity was observed. Although synthesis of alkaline phosphatase in biliary diversion rats was similar to that observed in control rats, biliary diversion rats showed 1.5-fold slower turnover of alkaline phosphatase when compared with control rats. These results suggest that conjugated bile salts in the intestinal lumen may cause a rapid turnover of brush border membrane hydrolases, which may be increased by the enhanced enzyme degradation. The mechanisms for the enhanced degradation appeared to be solubilization of hydrolases caused by the detergent activity of bile salts. Therefore, conjugated bile salts may play an important physiological role in the regulation of expression of the protease-resistant enzymes such as alkaline phosphatase.

Significant changes in intestinal lymphatic system and immune response elicited by Peyer's patch excision in adult rats

Abstract The effect of deprivation of Peyers patches (PP) on transport of lymphocytes through intestinal lymph and intestinal mucosal immune responses was investigated in rats. All visible PP in the rat small intestine were excised in order to examine the roles of PP in the intestinal lymphatic system and mucosal immune responses of the intestine. Two weeks after the experimental excision of PP, lymphocyte transport in intestinal lymph was significantly decreased in PP‐excised rats without significant changes in lymphocyte subsets as compared with sham operated control rats. Lymphocyte subsets as determined morphometrically in the intestinal mucosa showed no significant alteration in PP‐excised rats. There was a significant decrease in the number of immunoglobulin A (IgA) containing cells in the intestinal mucosa of PP‐excised rats, while IgM and IgG containing cells showed no statistically significant changes in number. Conversely, the macrophages in the intestinal mucosa increased in number, suggesting the enhanced accessory functions of these macrophages. Antigen‐specific immune response was further studied in PP‐excised rats using intraduodenal priming and challenge with cholera toxin (CT). Both the determinations of cells producing antigen‐specific antibody in the intestinal mucosa using anti‐CT antibody and those of cells secreting anti‐CT Ig in the intestinal lymph by enzyme‐linked immunospot (ELISPOT) assay showed a significant reduction of CT‐specific antibody production in PP‐excised rats compared with controls. Peyers patches appear to have an important role in lymphocyte transportation through intestinal lymph and also in mucosal immune responses.

Bile acid‐induced depolarization of mitochondrial membrane potential preceding cell injury in cultured gastric mucosal cells

Changes in energy metabolism elicited by sodium taurocholate and their relation to cell viability were determined in gastric mucosal cells. Cultured mucosal cells were labelled with rhodamine‐123, a mitochondrial energization‐sensitive fluorescence probe, or by propidium iodide, a fluorochrome which labels the nuclei of non‐viable cells. The cells were observed under a fluorescence microscope with a laser scanning confocal imaging system. After the addition of sodium taurocholate at concentrations > 5 mol/L, mucosal cells showed a rapid and significant decrease in rhodamine‐123 fluorescence. A decrease to 40% of the pretreated values at 30 min was seen with a concentration of sodium taurocholate of 7.5mmol/L. A marked increase in the percentage of propidium iodide‐positive cells was noted when the concentration of sodium taurocholate exceeded 5mmol/L. However, the extent of the decrease in rhodamine‐123 fluorescence was always greater than the increase in the percentage of propidium iodide‐positive cells, suggesting that most of these gastric mucosal cells remained viable. It is therefore suggested that the decrease in rhodamine‐123 fluorescence is largely due to the disturbed oxidative phosphorylation of mitochondria. Pretreatment of gastric mucosal cells with low concentrations of ethanol resulted in a significant cytoprotective effect against sodium taurocholate injury with significant prevention of a decrease in rhodamine‐123 fluoresence. It is concluded that sodium taurocholate induces a depolarization of the mitochondrial membrane potential preceding cell injury and that the cytoprotective effect of ethanol relates to its attenuation of the uncoupling effect.

The Effect of an Elemental Diet on Gut-Associated Lymphoid Tissue (Galt) in Rats

Intestinal gut-associated lymphoid tissue (GALT) IS constantly exposed to various antigenic stimuli in the gut lumen. Various dietary substances are known to have a great influence on the intestinal lymphatic system which plays an important role in intestinal mucosal immunity. For example, in our previous study,1 we reported that a remarkable increase in lymphocyte transport was induced during lipid adsorption in rat mesenteric lymphatics.