Biotransformation of theophylline in cirrhotic rats induced by biliary obstruction

Pharmacokinetics and metabolism of natural methylxanthines in animal and man

Caffeine, theophylline, theobromine, and paraxanthine administered to animals and humans distribute in all body fluids and cross all biological membranes. They do not accumulate in organs or tissues and are extensively metabolized by the liver, with less than 2% of caffeine administered excreted unchanged in human urine. Dose-independent and dose-dependent pharmacokinetics of caffeine and other dimethylxanthines may be observed and explained by saturation of metabolic pathways and impaired elimination due to the immaturity of hepatic enzyme and liver diseases. While gender and menstrual cycle have little effect on their elimination, decreased clearance is seen in women using oral contraceptives and during pregnancy. Obesity, physical exercise, diseases, and particularly smoking and the interactions of drugs affect their elimination owing to either stimulation or inhibition of CYP1A2. Their metabolic pathways exhibit important quantitative and qualitative differences in animal species and man. Chronic ingestion or restriction of caffeine intake in man has a small effect on their disposition, but dietary constituents, including broccoli and herbal tea, as well as alcohol were shown to modify their plasma pharmacokinetics. Using molar ratios of metabolites in plasma and/or urine, phenotyping of various enzyme activities, such as cytochrome monooxygenases, N-acetylation, 8-hydroxylation, and xanthine oxidase, has become a valuable tool to identify polymorphisms and to understand individual variations and potential associations with health risks in epidemiological surveys.

Synthesis, pharmacological activity and nitric oxide generation by nitrate derivatives of theophylline

Nitrates of theophylline derivatives — potential nitric oxide (NO) donors — were synthesized by esterification of 7-hydroxyalkyl theophylline derivatives with fuming nitric acid. The nitrates obtained were tested in-vitro in reactions with sulfydryl compounds at appropriately adjusted pH and temperature. Under the applied conditions, the synthesized compounds underwent decomposition to release NO, quantified using a polarographic method using a selective isolated (ISO-NO) sensor. The effects of dyphylline and proxyphylline and their new synthesized nitrates on arterial blood pressure (BP) were measured in spontaneously hypertensive (SH) rats. BP was measured in conscious SH rats using the tail-cuff method. Both short- and long-term administration of the xanthines tested significantly decreased systolic, diastolic and mean BP. The hypotensive effect of a single dose of nitrate dyphylline on mean BP was greater than that of the parent compound (P = 0.000012; P = 0.000472 at 30 and 60 min post-dose, respectively), whereas proxyphylline and its nitrate derivative had similar activity. In rats treated with the tested compounds for 9 days twice daily, the decrease in BP persisted for at least 16 h after the last dose. Proxyphylline produced the most marked decrease in diastolic and mean BP. Among the xanthines examined, proxyphylline nitrate had the strongest hypotensive effect when administered in a single dose to animals pretreated with the same compound for 9 days. These results indicate that insertion of a nitrate group weakly modifies the hypotensive action of the studied xanthines in SH rats.

An acqueous extract of Bidens pilosa L. protects liver from cholestatic disease: experimental study in young rats

PURPOSE: To test the hepatoprotective effect of water extract from Bidens Pilosa L. (BPE) in cholestatic liver disease induced by ligature and resection of the common bile ducts (LRBD) in young rats. METHODS: We studied four groups of ten 21 days old (P21) Wistar rats, Group SW: sham operation and water; Group SD: sham operation and BPE (160 mg of fresh leaves/100 g of body weight/day); Group LW: LRBD and water and Group LD: LRBD and BPE daily. Pentobarbital sleeping time (PST) and serum activities of aspartate aminotransferase (AST) and of alanine aminotransferase (ALT) were determined after the sacrifice (P70). A Ruwart's score for hepatic fibrosis (RS) was given to each animal. Were employed two way ANOVA and the test of Tukey or a non-parametric test for multiple comparisons. RESULTS: There were statistically significant differences between LW and LD in the measurements of the PST ((means LW=390; LD=173), AST (means LW=8, LD=5), ALT (medians LW=2; LD=1) e RS (medians LW=2; LD=1). CONCLUSION: BPE could be used in the phytotherapy of the hepatic damage induced by chronic obstructive cholestasis, because protects liver function, decreases the rate of necrosis and liver fibrosis in cholestatic liver disease.

The increment of purine specific sodium nucleoside cotransporter mRNA in experimental fibrotic liver induced by bile duct ligation and scission

We investigated the expression profiles of rat fibrotic liver induced by bile duct ligation and scission (BDL/S) using the 3'-directed cDNA libraries. The possibility that the 3'directed cDNA library represents the mRNA population faithfully was examined by northern blots. During the northern analysis based on fibrotic liver expression profile, we found for the first time that purine specific sodium nucleoside cotransporter (SPNT) was upregulated in BDL/S-induced fibrotic liver. To determine whether the accumulation of bile juice could affect the expression of SPNT mRNA or not, we examined the change of SPNT mRNA expression at 3, 14, 28 days after BDL/S operation. No change in SPNT expression was observed in rat liver at 3 days after surgery. In contrast, there were significant increases in SPNT expression at 14 and 28 days after surgery. We also examined whether chronic liver damage affected SPNT mRNA expression. SPNT mRNA level was significantly increased in BDL/S-induced fibrotic rat liver, whereas no significant change was obserbed in fibrotic livers chronically exposed to carbon tetrachloride or dimethylnitrosamine. From the above results, although further study might be needed, it was considered that the increment of SPNT mRNA in BDL/S liver morphological compatibility to human was remarkable.

Antifibrotic effect of Stephania tetrandra on experimental liver fibrosis induced by bile duct ligation and scission in rats

We examined the antifibrotic effect of a methanol extract from Stephania tetrandra (ST) on experimental liver fibrosis. Liver fibrosis was induced by bile duct ligation and scission (BDL/S) in rats. In BDL/S rats, activity levels of aspartate transaminase (AST), alanine transaminse (ALT), alkaline phosphatase (ALP), concentration of total bilirubin in serum, and hydroxyproline content of the liver were significantly increased. The ST treatment (either 100 mg/kg/day or 200 mg/kg/day, p.o. for 4 weeks) in BDL/S rats reduced the serum AST, ALT and ALP activity levels significantly (p< 0.01). Similarly, when compared to the control group, the concentration of hydroxyproline in the livers of the BDL/S rats treated with 100mg or 200mg ST treated rats decreased by 40% and 33% respectively, when compared to the BDL/S control group (p<0.01). The morphological characteristics of fibrotic liver that were observed in the BDL/S control group, improved in the ST treated BDL/S group. In the fibrotic liver of BDL/S rats treated with ST, a marked reduction in the numbers of alpha smooth muscle cell actin positive stellate cells was observed. These results indicate that doses of either 100 or 200 mg/kg/day of methanol extract from S. tetrandra, had an antifibrotic effect in rats with liver fibrosis induced by bile duct ligation and scission.