Role of metabolism by intestinal microbiota in pharmacokinetics of oral baicalin.

Baicalin (baicalein-7-glucuronide) is a flavonoid purified from Scutellaria baicalensis Georgi that has traditionally been used for treatment of hypertension, cardiovascular diseases, and viral hepatitis. In this study, the effects of intestinal microbiota on the pharmacokinetics of baicalin were investigated in normal and antibiotic-pretreated rats following p.o. administration of 100 mg/kg baicalin by using liquid chromatography/ion trap mass spectrometry. When rats were pretreated orally with cefadroxil, oxytetracycline and erythromycin for 3 days to control the number of intestinal bacteria, the pharmacokinetic parameters of oral baicalin were significantly affected by antibiotics: Cmax, T1/2(ß), Kel and AUC values were significantly changed compared to those in normal rats. These results indicate that intestinal microbiota might play a key role in the oral pharmacokinetics of baicalin.

Role of metabolism in 1-bromopropane-induced hepatotoxicity in mice.

A possible role of metabolism in 1-bromopropane (1-BP)-induced hepatotoxicity was investigated in male ICR mice. The depletion of glutathione (GSH) by formation of GSH conjugates was associated with increased hepatotoxicity in 1-BP-treated mice. The formation of S-propyl and 2-hydroxypropyl GSH conjugates were identified in the liver following 1-BP treatment. In addition, the formation of reactive metabolites of 1-BP by certain cytochrome P-450 (CYP) may be involved in 1-BP-induced hepatotoxicity. The decreased content of hepatic GSH produced by 1-BP was associated not only with increased activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) but also with elevated levels of hepatic thiobarbituric acid-reactive substance (TBARS) in mice where metabolic enzymes were induced by pretreatment with phenobarbital. In addition, the hepatotoxicity induced by 1-BP was prevented by pretreatment with SKF-525A. Taken together, the formation of reactive metabolites by CYP and depletion of GSH may play important roles in hepatotoxicity induced by 1-BP.

Role of glutathione conjugation in 1-bromobutane-induced hepatotoxicity in mice.

Halogenated organic compounds, such as 1-bromobutane (1-BB), have been used as cleaning agents, agents for chemical syntheses, or extraction solvents. In the present study, hepatotoxic effects of 1-BB and its conjugation with glutathione (GSH) were investigated in female BALB/c mice. Animals were treated orally with 1-BB at 375, 750 and 1500 mg/kg in corn oil once for dose-response study or treated orally with 1-BB at 1500 mg/kg for 6, 12, 24 and 48h for time-course study. Three kinds of GSH conjugates, including S-butyl GSH, S-butyl cysteine, and (hydroxybutyl)mercapturic acid, were identified in livers by liquid chromatography-electrospray ionization-tandem mass spectrometry. When the production of S-butyl GSH from 1-BB was investigated in the liver, the conjugate was detected maximally 6h after treatment. Hepatic GSH levels were almost depleted by single treatment with 1-BB within 6h. Treatment of mice with 1-BB increased in serum activities of alanine aminotransferase and aspartate aminotransferase dose-dependently. Hepatic contents of thiobarbituric acid reactive substances were significantly increased by 1-BB at 12 and 24h after treatment. Our present results suggested that 1-BB could cause hepatotoxicity as well as depletion of GSH content, due to the formation of GSH conjugates with 1-BB in mice.

Role of Glutathione Conjugation in 1-Bromobutane-induced Immunotoxicity in Mice.

Halogenated organic compounds, such as 1-bromobutane (1-BB) , have been used as cleaning agents, agents for chemical syntheses or extraction solvents in workplace. In the present study, immunotoxic effects of 1-BB and its conjugation with glutathione (GSH) were investigated in female BALB/c mice. Animals were treated orally with 1-BB at 375, 750 and 1500 mg/kg in corn oil once for dose response or treated orally with 1-BB at 1500 mg/kg for 6, 12, 24 and 48 hr for time course. S-Butyl GSH was identified in spleen by liquid chromatography-electrospray ionization tandem mass spectrometry. Splenic GSH levels were significantly reduced by single treatment with 1-BB. S-Butyl GSH conjugates were detected in spleen from 6 hr after treatment. Oral 1-BB significantly suppressed the antibody response to a T-dependent antigen and the production of splenic intracellular interlukin-2 in response to Con A. Our present results suggest that 1-BB could cause immunotoxicity as well as reduction of splenic GSH content, due to the formation of GSH conjugates in mice. The present results would be useful to understand molecular toxic mechanism of low molecular weight haloalkanes and to develop biological markers for exposure to haloalkanes.