Biliary excretion of essential trace elements in rats under oxidative stress caused by selenium deficiency.

The excretion of essential trace elements, namely, Se, Sr, As, Mn, Co, V, Fe, and Zn into the bile of Se-deficient (SeD) Wistar male rats was studied using the multitracer (MT) technique, and instrumental neutron activation analysis (INAA). Normal and Se-control (SeC) rat groups were used as reference groups to compare the effects of Se levels on the behaviors of the essential trace elements. The excretion (% dose) of Se, Sr, As, Mn, Co, and V increased with Se levels in the liver. The biliary excretion of Mn and As dramatically enhanced for SeC rats compared with SeD rats, while that of V accelerated a little for SeC rats. The radioactivity levels of (59)Fe and (65)Zn in the MT tracer solution were insufficient to measure their excretion into bile. The role of glutathione and bilirubin for biliary excretion of the metals was discussed in relation to Se levels in rat liver.

Study of thermodynamic parameters for solubilization of plant sterol and stanol in bile salt micelles.

We investigated the difference between the molecular structures of plant sterols and stanols that affect the solubilization of cholesterol in bile salt micelles (in vitro study). First, the aqueous solubility of beta-sitosterol, beta-sitostanol, and campesterol was determined by considering the specific radioactivity by using a fairly small quantity of each radiolabeled compound. The order of their aqueous solubilities was as follows: cholesterol > campesterol > beta-sitostanol > beta-sitosterol. The maximum solubility of cholesterol and the above mentioned sterol/stanol in sodium taurodeoxycholate and sodium taurocholate solutions (single solubilizate system) was measured. Moreover, the preferential solubilization of cholesterol in bile salt solutions was systematically studied by using different types of plant sterols/stanols. The solubilization results showed that the cholesterol-lowering effect was similar for sterols and stanol. Thermodynamic analysis was applied to these experimental results. The Gibbs energy change (Delta G degrees ) for the solubilization of plant sterols/stanols showed a negative value larger than that for cholesterol.

Changes in the components of biliary and plasma lipids in selenium-deficient rats.

We constructed a chronic oxidative stress model in which Se-deficient diet was fed to male Wister rats for 8 weeks. As expected, effects of oxidative damage, including Fe accumulation and increase in peroxidized lipids, were identified in the liver owing to the lack of glutathione peroxidase. Although the oxidative stress caused Fe accumulation in the liver, the Fe concentration in bile of the SeD rat was almost the same as that in the control rats. The constant excretion of Fe into bile supported the Fe accumulation in the liver. No differences were observed in the principal components of biliary lipids, i.e., bile acids, phospholipids, and cholesterol, between the two groups; moreover, these trends were also reflected in the plasma. Due to the trapping of reactive oxygen species, only bilirubin concentrations in the bile and plasma were decreased in the SeD group, when compared with those in the control group. Measurement of bilirubin concentration may be used as a supplemental oxidative stress marker.

Light irradiation is a factor in the bactericidal activity of silver-loaded zeolite.

Silver loaded zeolite (Ag-Z) was previously found to have effective bactericidal activity against Escherichia coli. To understand the mechanisms of bactericidal activity of Ag-Z, role of light irradiation was focused and investigated in this study. In this study, we focused on light irradiation. Antibacterial assay and spectroscopic study revealed that light irradiation enabled Ag-Z to reduce dioxygen to form a reactive oxygen species, which led to bactericidal activity. These results indicate that the onset of bactericidal activity can be controlled by light irradiation.