Pharmacokinetics of chlorogenic acid and corydaline in DA-9701, a new botanical gastroprokinetic agent, in rats.

1.Few studies describing the pharmacokinetic properties of chlorogenic acid (CA) and corydaline (CRD) which are marker compounds of a new prokinetic botanical agent, DA-9701, have been reported. The aim of the present study is to evaluate the pharmacokinetic properties CA and CRD following intravenous and oral administration of pure CA (1-8 mg/kg) or CRD (1.1-4.5 mg/kg) and their equivalent dose of DA-9701 to rats. 2. Dose-proportional AUC and dose-independent clearance (10.3-12.1 ml/min/kg) of CA were observed following its administration. Oral administration of CA as DA-9701 did not influence the oral pharmacokinetic parameters of CA. Incomplete absorption of CA, its decomposition in the gastrointestinal tract, and/or pre-systemic metabolism resulted in extremely low oral bioavailability (F) of CA (0.478-0.899%). 3. CRD showed greater dose-normalized AUC in the higher dose group than that in lower dose group(s) after its administration due to saturation of its metabolism via decreased non-renal clearance (by 51.3%) and first-pass extraction. As a result, the F of CRD following 4.5 mg/kg oral CRD (21.1%) was considerably greater than those of the lower dose groups (9.10 and 13.8%). However, oral administration of CRD as DA-9701 showed linear pharmacokinetics as a result of increased AUC and F in lower-dose groups (by 182% and 78.5%, respectively) compared to those of pure CRD. The greater oral AUC of CRD for DA-9701 than for pure CRD could be due to decreased hepatic and/or GI first-pass extraction of CRD by other components in DA-9701.

Effects of 17α-ethynylestradiol-induced cholestasis on the pharmacokinetics of doxorubicin in rats: reduced biliary excretion and hepatic metabolism of doxorubicin.

1. Since the prevalent hormonal combination therapy with estrogen analogues in cancer patients has frequency and possibility to induce the cholestasis, the frequent combination therapy with 17α-ethynylestradiol (EE, an oral contraceptive) and doxorubicin (an anticancer drug) might be monitored in aspect of efficacy and safety. Doxorubicin is mainly excreted into the bile via P-glycoprotein (P-gp) and multidrug resistance-associated protein 2 (Mrp2) in hepatobiliary route and metabolized via cytochrome P450 (CYP) 3A subfamily. Also the hepatic Mrp2 (not P-gp) and CYP3A subfamily levels were reduced in EE-induced cholestatic (EEC) rats. Thus, we herein report the pharmacokinetic changes of doxorubicin with respect to the changes in its biliary excretion and hepatic metabolism in EEC rats. 2. The pharmacokinetic study of doxorubicin after intravenous administration of its hydrochloride was conducted along with the investigation of bile flow rate and hepatobiliary excretion of doxorubicin in control and EEC rats. 3. The significantly greater AUC (58.7% increase) of doxorubicin in EEC rats was due to the slower CL (32.9% decrease). The slower CL was due to the reduction of hepatic biliary excretion (67.0% decrease) and hepatic CYP3A subfamily-mediated metabolism (21.9% decrease) of doxorubicin. These results might have broader implications to understand the altered pharmacokinetics and/or pharmacologic effects of doxorubicin via biliary excretion and hepatic metabolism in experimental and clinical estrogen-induced cholestasis.

Effects of ACE and ADD1 gene polymorphisms on blood pressure response to hydrochlorothiazide: a meta-analysis.

Hydrochlorothiazide (HCTZ) is used to treat uncomplicated hypertension. However, many studies have reported the variance of inter-individual response to HCTZ. A meta-analysis of published data was conducted to evaluate the pharmacogenetic associations of ACE I/D and ADD1 Gly460Trp polymorphisms with blood pressure changes during HCTZ therapy. To analyze the influence of ACE I/D polymorphism, 4 studies including 1,439 patients were assessed and the 3 genotypes were compared (II vs. ID, II vs. DD, and ID vs. DD) with respect to blood pressure changes. A significant association between ACE and blood pressure change was observed for the comparison of the II and DD (standard differences in means = 0.256; 95% CI, 0.109 - 0.403). For ADD1 Gly460Trp polymorphism, 4 studies including 1,001 patients were assessed, and GlyGly vs. GlyTrp, GlyGly vs. TrpTrp and GlyTrp vs. TrpTrp genotype comparisons were analyzed. A significant association between ADD1 and blood pressure change was observed for the comparisons of GlyGly vs. GlyTrp (standard differences in means= 2.78; 95% CI, 0.563 - 4.99) and GlyGly vs. TrpTrp (standard differences in means = 1.80; 95% CI, 1.38 - 2.22). This study is the first meta-analysis to evaluate the influences of ACE and ADD1 polymorphisms on blood pressure responses to HCTZ to combine the inconsistent results of previous studies.

Effects of cysteine on the pharmacokinetics of docetaxel in rats with protein-calorie malnutrition.

The objective of this study is to report the effects of cysteine on the pharmacokinetics of intravenous and oral docetaxel in rats with protein-calorie malnutrition (PCM). The in vivo pharmacokinetics and in vitro hepatic/intestinal metabolism of docetaxel were assessed using control, CC (control with cysteine), PCM and PCMC (PCM with cysteine) rats. The effects of cysteine on the intestinal absorption of docetaxel were further investigated through in vitro transport studies using rat intestine and Caco-2 cell monolayers. The AUCs (the areas under the plasma concentration-time curve from time zero to time infinity) of intravenous docetaxel in PCM rats were significantly greater than in the control rats because of the significant decrease in the hepatic CYP3A. In PCMC rats, the elevated AUCs in PCM rats returned to control levels. The AUC(0-6 h)s of oral docetaxel in PCM rats were significantly smaller than that in the control rats, mainly due to the decrease in gastrointestinal absorption. In CC and PCMC rats, oral cysteine supplement enhanced the gastrointestinal absorption of docetaxel probably via intestinal P-gp inhibition. If the present rat data could be expressed to humans, the alterations in docetaxel absorption and metabolism should be considered in designing a dosage regimen for cancer patients with PCM state after cysteine supplement.

Effects of cysteine on the pharmacokinetics of tamoxifen in rats with protein-calorie malnutrition.

Protein-calorie malnutrition (PCM) could occur frequently in cancer patients and alter the pharmacokinetics of drugs. Also cysteine shows anti-oxidative effect and changes the activities of drug metabolizing enzyme and/or transporters. Herein, we investigated the effects of cysteine on the pharmacokinetics of tamoxifen in rats with protein-calorie malnutrition (PCM). The in vivo pharmacokinetics and in vitro hepatic/intestinal metabolism of tamoxifen were assessed using control, CC (control with cysteine), PCM, PCMC (PCM with cysteine) rats. The effects of cysteine on the intestinal absorption of tamoxifen were further investigated through in vitro transport studies using rat intestine. The AUCs of intravenous tamoxifen in PCM rats were significantly greater than control rats due to the decrease in the hepatic metabolism via CYP3A. In PCMC rats, the elevated AUCs in PCM rats returned to control levels by oral cysteine supplement. The AUC of oral tamoxifen in PCM rats was significantly smaller than in control rats mainly due to the decrease in gastrointestinal absorption. In CC and PCMC rats, oral cysteine supplement enhanced the gastrointestinal absorption of tamoxifen probably via intestinal P-gp inhibition. The present study demonstrated that PCM state and/or oral cysteine supplement had a profound impact on the pharmacokinetics of tamoxifen in rats. If the present rat data are extrapolated to humans, the alterations in tamoxifen absorption and metabolism should be considered in designing a dosage regimen for cancer patients with PCM and/or oral cysteine supplement.

Pharmacokinetics of verapamil and its metabolite norverapamil in rats with hyperlipidaemia induced by poloxamer 407.

In this study, the pharmacokinetics of verapamil and its active metabolite norverapamil were evaluated following intravenous and oral administration of 10 mg/kg verapamil to rats with hyperlipidaemia (HL) induced by poloxamer 407 (HL rats). The total area under the plasma concentration time curve (AUC) of verapamil in HL rats following intravenous administration was significantly greater (by 11.2%) than in control rats due to their slower (by 11%) non-renal clearance. The oral AUC of verapamil in HL rats was also significantly greater (by 116%) compared with controls, with a larger magnitude than the data observed following intravenous administration. This may have been a result of the decreased intestinal metabolism of verapamil in HL rats. The AUC of norverapamil and AUC(norverapamil)/AUC(verapamil) ratios following intravenous and oral administration of verapamil were unchanged in HL rats. Assuming that the HL rat model qualitatively reflects similar changes in patients with HL, the findings of this study have potential therapeutic implications. Further studies in humans are required to determine whether modification of the oral verapamil dosage regimen in HL states is necessary.

Pharmacokinetic interaction between metoprolol and SP-8203 in rats: competitive inhibition for the metabolism of metoprolol by SP-8203 via hepatic CYP2D subfamily.

1. The occurrence of cerebral ischemia is prevalent in patients with hypertension and the combination drug therapy is needed. Thus, the pharmacokinetic interaction between metoprolol (anti-hypertension drug) and SP-8203 (a new drug candidate for cerebral ischemia) with respect to the metabolism via CYP isozymes was evaluated. 2. Metoprolol and SP-8203 were administered intravenously or orally to rats. Concentrations (I) of each drug in the liver and intestine in in vivo studies, the disappearance and apparent K(i) of each drug in in vitro microsomes and [I]/K(i) ratios for each drug were determined. In addition, the disappearance of each drug via CYPs in rat and human microsomes were measured. 3. The AUC and CL(NR) of intravenously administered metoprolol with SP-8203 were significantly greater and slower, respectively, than without SP-8203. However, pharmacokinetic parameters of oral metoprolol and intravenous/oral SP-8203 were not altered. 4. The hepatic metabolism of metoprolol via CYP2D was inhibited by SP-8203 in a competitive manner. However, the intestinal metabolism of metoprolol was not influenced by SP-8203. SP-8203 was not metabolized via CYP isozymes in rats and then co-administration of metoprolol did not affect the metabolism of SP-8203.

Pharmacokinetics and first-pass metabolism of astaxanthin in rats.

Astaxanthin is a carotenoid with antioxidant, anti-cancer and anti-inflammatory properties. The pharmacokinetics of astaxanthin after its intravenous (5, 10, and 20 mg/kg) and oral (100 and 200 mg/kg) administration and its first-pass extraction ratios after its intravenous, intraportal or intragastric (20 mg/kg) administration were evaluated in rats. The pharmacokinetic parameters of astaxanthin were dose dependent after its intravenous administration, due to the saturable hepatic metabolism of astaxanthin, but dose independent after oral administration. The gastrointestinal absorption of astaxanthin followed the flip-flop model. The hepatic and gastrointestinal first-pass extraction ratios of astaxanthin were approximately 0·490 and 0·901, respectively. Astaxanthin was metabolised primarily by hepatic cytochrome P-450 1A1/2 in rats. Astaxanthin was unstable up to 4 h incubation in four rat gastric juices and up to 24 h incubation in various buffer solutions having a pH of 1-13. The tissue/plasma ratios of astaxanthin at 8 and 24 h after its oral administration (100 mg/kg) were greater than unity for all tissues studied, except in the heart, at 8 h, indicating that the rat tissues studied had high affinity for astaxanthin.

Pharmacokinetics of mirodenafil, a new erectogenic, and its metabolite, SK3541, in rats: involvement of CYP1A1/2, 2B1/2, 2D subfamily, and 3A1/2 for the metabolism of both mirodenafil and SK3541.

PURPOSE: This study was performed to find which types of hepatic CYP isoforms are responsible for the metabolism of mirodenafil (a new erectogenic) and one of its metabolite, SK3541, using various hepatic CYP inducers and inhibitors in rats. METHODS: Mirodenafil at a dose of 20 mg/kg was administered intravenously to control rats and rats pretreated with various CYP inducers and inhibitors. The disappearance of SK3541 was also measured in vitro hepatic microsomes of rats with and without CYP inducer and inhibitors. RESULTS: Compared to controls, in rats pretreated with 3-methylcholanthrene, orphenadrine, and dexamethasone (main inducers of CYP1A1/2, 2B1/2, and 3A1/2, respectively), the non-renal clearances (CLNRs) of mirodenafil were significantly faster (by 39.4%, 59.3%, and 63.9%, respectively). However, compared to controls, in rats pretreated with quinine and troleandomycin (main inhibitors of CYP2D subfamily and 3A1/2, respectively), the CLNRs of mirodenafil were significantly slower (by 36.1% and 33.2%, respectively). In rat hepatic microsomes spiked with furafylline, quinine, and troleandomycin (main inhibitors of CYP1A2, 2D subfamily, and 3A1/2, respectively), the intrinsic clearances (CLints) for the disappearance of SK3541 were significantly slower (by 18.4%, 35.3%, and 51.5%, respectively) than controls. Also in rat hepatic microsomes pretreated with orphenadrine (a main inducer of CYP2B1/2), the CLint for the disappearance of SK3541 was significantly faster (by 55.5%) than controls. CONCLUSIONS: The above data suggest that hepatic CYP1A1/2, 2B1/2, 2D subfamily, and 3A1/2 are involved in the metabolism of both mirodenafil and SK3541 in rats.

Pharmacokinetic interaction between oltipraz and silymarin in rats.

PURPOSE: To evaluate the pharmacokinetic interaction between oltipraz and silymarin after intravenous and oral administration of both drugs to male Sprague-Dawley rats. METHODS: Oltipraz (single doses of 10 and 30 mg/kg for intravenous and oral administration, respectively), silymarin (single doses of 50 and 100 mg/kg for intravenous and oral administration, respectively, and 14 days oral administration of 100 mg/kg), alone and together were administered to control rats. RESULTS: The pharmacokinetic parameters of oltipraz did not significantly altered by silymarin. However, after intravenous administration of the drugs together, the AUCs of unconjugated, conjugated, and total (unconjugated plus conjugated) silibinin were significantly different (32.7% decrease, and 32.1% and 27.2% increase, respectively), and total and (CL) and non-renal (CL NR ) clearance of unconjugated silibinin were significantly faster (49.4% and 61.1% increase, respectively) than those of silymarin alone (without oltipraz). After oral administration of silymarin with or without oltipraz, however, the pharmacokinetic parameters of unconjugated, conjugated, and total silibinin were comparable. CONCLUSIONS: After single intravenous administration of the drugs together, the AUC of unconjugated silibinin was significantly smaller, but that of both conjugated and total silibinin was significantly greater. This could have been due to an increase in the formation of conjugates (glucuronidation and sulfation) of silibinin as induced by oltipraz. After simultaneous oral administration of the drugs, however, the AUCs (or AUC 0-12 h) of unconjugated, conjugated, and total silibinin were comparable.

Effects of endotoxin derived from Escherichia coli lipopolysaccharide on the pharmacokinetics of drugs.

Lipopolysaccharide (LPS) endotoxin is an active component in the outer membrane of Gram-negative bacteria. LPS is usually used as an animal model of chronic inflammation such as sepsis. During inflammation, development of diarrhea, and changes in the plasma protein bindings, in the hepatic and/or intestinal microsomal cytochrome P450 (CYP) isozymes, and in the renal excretion of drugs have been reported. Thus, in rats pretreated with lipopolysaccharide endotoxin isolated from Escherichia Coli (ECLPS rats), the absorption, the distribution, the metabolism, and the excretion of drugs could be expected to alter. Interestingly, in ECLPS rats, the time-dependent effects on the hepatic CYP isozymes have been reported. Thus, in ECLPS rats, the pharmacokinetics of drugs which are mainly metabolized via hepatic CYP isozymes could be expected to be time-dependent. In this review, an attempt to explain changes in the pharmacokinetics of drugs reported in the literature was made in terms of hepatic CYP isozyme changes or urinary excretion changes in ECLPS rats.

Effects of water deprivation on drug pharmacokinetics: correlation between drug metabolism and hepatic CYP isozymes.

Male Sprague-Dawley rats deprived of water for 72 h (a rat model of dehydration) showed no change in protein expression of the hepatic microsomal cytochrome P450 (CYP) 1A2, 2B1/2, 2C11, or 3A1/2, but an increase in protein expression (3-fold) and mRNA level (2.6-fold) of CYP2E1. Glucose feeding instead of food normalized CYP2E1 protein expression during dehydration. Here, we review how dehydration can change the pharmacokinetics of drugs reported in the literature via changing CYP isozyme levels. We also discuss how dehydration changes the pharmacokinetics of drugs that are metabolized via renal DHP-I, or are mainly excreted in the urine and bile, and form conjugates.

Dose-dependent pharmacokinetics of telithromycin after intravenous and oral administration to rats: contribution of intestinal first-pass effect to low bioavailability.

PURPOSE: To evaluate the pharmacokinetics of telithromycin after intravenous and oral administration and to find the reason for incomplete F value (first pass-effect) after intravenous, intraportal, intragastric, and intraduodenal administration to rats. METHODS: Telithromycin was administered intravenously or orally at doses of 20, 50, and 100 mg/kg to rats. And hepatic, gastric, and intestinal first-pass effects of telithromycin were also measured after intravenous, intraportal, intragastric, and intraduodenal administration at a dose of 50 mg/kg to rats. RESULTS: The dose-normalized AUC values of telithromycin were dose-dependent (increased with increasing doses) after both intravenous and oral dose ranges studied, possibly due to saturable metabolism of telithromycin. After oral administration (50 mg/kg), approximately 4.06% of oral dose was not absorbed, F was approximately 27.5%, and the intestinal first-pass effect was approximately 63.4% of oral dose. The first-pass effects of telithromycin in the lung, heart, stomach, and liver were almost negligible, if any, in rats. CONCLUSIONS: The low F of telithromycin at a dose of 50 mg/kg was mainly due to considerable intestinal first-pass effect, approximately 63.4% of oral dose, in rats.

Effects of glucose supplementation on the pharmacokinetics of intravenous chlorzoxazone in rats with water deprivation for 72 h.

It was reported that in rats with water deprivation for 72 h with food (dehydration rat model), the expression of CYP2E1 was 3-fold induced with an increase in mRNA level and glucose supplementation instead of food during 72-h water deprivation (dehydration rat model with glucose supplementation) inhibited the CYP2E1 induction in dehydration rat model. It was also reported that chlorzoxazone (CZX) is metabolized to 6-hydroxychlorzoxazone (OH-CZX) mainly via CYP2E1 in rats. Hence, the effects of glucose supplementation on the pharmacokinetics of CZX and OH-CZX were investigated after intravenous administration of CZX at a dose of 25 mg/kg to control male Sprague-Dawley rats and dehydration rat model and dehydration rat model with glucose supplementation. Based on the above mentioned results of CYP2E1, it could be expected that increased formation of OH-CZX in dehydration rat model could decrease in dehydration rat model with glucose supplementation. This was proven by the following results. In dehydration rat model with glucose supplementation, the AUC of OH-CZX was significantly smaller (1900 versus 1050 microg min/ml), AUC(OH-CZX)/AUC(CZX) ratio was considerably smaller (105 versus 34.3%), C(max) was significantly lower (20.6 versus 8.08 microg/ml), total amount excreted in 24-h urine as unchanged OH-CZX was significantly smaller (62.3 versus 42.7% of intravenous dose of CZX), and in vitro V(max) (2.18 versus 1.20 nmol/min/mg protein) and CL(int) (0.0285 versus 0.0171 ml/min/mg protein) were significantly slower than those in dehydration rat model.

Pharmacokinetics of oltipraz in rat models of diabetes mellitus induced by alloxan or streptozotocin.

Pharmacokinetic parameters of oltipraz were compared after intravenous (10 mg/kg) and oral (30 mg/kg) administration in rat model of diabetes mellitus induced by alloxan (rat model of DMIA) or streptozotocin (rat model of DMIS) and their respective control male Sprague-Dawley rats. In rat models of DMIA and DMIS, the expressions and mRNA levels of CYP1A2, 2B1/2, and 3A1(23) increased, and oltipraz was metabolized mainly via CYP1A1/2, 2B1/2, 2C11, 2D1, and 3A1/2 in male Sprague-Dawley rats. Hence, it would be expected that the AUC and CL values of oltipraz would be significantly smaller and faster, respectively, in rat models of diabetes. This was proven by the following results. After intravenous administration, the AUC values were significantly smaller in rat models of DMIA (40.1% decrease) and DMIS (26.0% decrease) than those in respective control rats, and this could be due to significantly faster CL values in rat models of DMIA (40.1% increase) and DMIS (26.0% increase). The faster CL could be due to increase in hepatic blood flow rate and significantly faster CL(int) in rat models of diabetes, since oltipraz is an intermediate hepatic extraction ratio drug in male Sprague-Dawley rats. After oral administration, the AUC values of oltipraz were also significantly smaller in rat models of DMIA (54.0% decrease) and DMIS (63.2% decrease). This could be due to increase in hepatic blood flow rate, significantly faster CL(int), and changes in the intestinal first-pass effect in rat models of diabetes. However, this was not due to decrease in absorption in rat models of diabetes.

Effects of water deprivation on the pharmacokinetics of DA-8159, a new erectogenic, in rats.

PURPOSE: To test the effect of 72 h water deprivation on the non-renal clearance (CL) of DA-8159 in a rat model of dehydration. DA-8159 is mainly metabolized via CYP3A1/2 and the expression and mRNA level of CYP3A1/2 are not affected by dehydration. METHODS: DA-8159 (30 mg/kg) was administered intravenously or orally to male control Sprague Dawley rats and rat model of dehydration. RESULTS: As expected, after intravenous administration, the CL(NR) values of DA-8159 were comparable between two groups of rats. This could be supported by comparable intrinsic CL of DA-8159 using hepatic microsomes for both groups of rats. However, the CL was significantly slower in rat model of dehydration due, at least in part, to significantly slower renal CL in rat model of dehydration. The slower CL(R) in rat model of dehydration could be due to urine flow ratedependent renal CL of DA-8159; the less urine output, the less the urinary excretion of unchanged DA-8159. After oral administration, the AUC values of DA-8159 were not significantly different between two groups of rats, although the AUC of DA-8159 in rat model of dehydration was significantly greater than controls after intravenous administration. This could be possibly due to changes in the intestinal first-pass effects in rat model of dehydration. CONCLUSIONS: After intravenous administration of DA-8159, the non-renal CL values were comparable between two groups of rats due to the lack of effect of dehydration on CYP3A1/2.

Repression by oxidative stress of iNOS and cytokine gene induction in macrophages results from AP-1 and NF-kappaB inhibition mediated by B cell translocation gene-1 activation.

Previously, we reported that oxidative stress caused by sulfur amino acid deficiency (SD) induces B cell translocation gene-1 (Btg-1), which belongs to the Apro family, in hepatocytes. In view of the impairment of immune function by protein restriction that causes SD, this study investigated whether SD or other oxidative stress inhibits iNOS and cytokine expression and induces Btg-1 in macrophages and explored the causal relationship of Btg-1 induction and repression of the genes. When macrophages were incubated in sulfur amino acid-deprived medium, lipopolysaccharide induction of iNOS, TNFalpha, IL-1beta, and IL-6 was significantly decreased compared to control. Because AP-1 and NF-kappaB are the common transcription factors that regulate the genes encoding iNOS and cytokines, we examined AP-1 and NF-kappaB DNA binding activities and transactivation of the iNOS gene containing the DNA binding elements. Induction of the reporter gene pGL-miNOS-1588 comprising the -1.6 kb iNOS promoter in lipopolysaccharide-activated macrophages was inhibited 30-70% by SD or treatment with pro-oxidants, including tert-butylhydroxyquinone, buthionine sulfoximine, and 3-morpholinosydnonimine. Oxidative stress increased Btg-1 mRNA. SD-induced oxidative stress activated Btg-1 in macrophages, as evidenced by nuclear translocation of endogenous or green fluorescent protein-tagged Btg-1, which localized in the cytoplasm in the resting state. Expression of Btg-1 inhibited lipopolysaccharide-inducible AP-1 and NF-kappaB activities, repressing transactivation of the target gene pGL-miNOS-1588. These results provide evidence that oxidative stress induced by SD or pro-oxidants inhibits the expression of iNOS and cytokines in macrophages with Btg-1 activation and that the gene repression by oxidative stress may result from Btg-1-mediated inhibition of AP-1 and NF-kappaB activities.

Oltipraz regenerates cirrhotic liver through CCAAT/enhancer binding protein-mediated stellate cell inactivation.

Liver cirrhosis (LC) is a chronic disease with high mortality rate. In the United States and Western world as well as Asian countries, LC is the major leading cause of death by disease. Yet, no effective therapeutic agent is available for LC treatment. Laboratory cirrhotic rats produced by dimethylnitrosamine administrations simulate the clinical features of human LC such as mortality, ascites, hepatic parenchymal cell destruction, and formation of connective tissue and nodular regeneration, providing a preclinical model to evaluate therapeutic efficacy of drugs and the underlying mechanisms. Oltipraz [5-(2-pyrazinyl)-4-methyl-1,2-dithiol-3-thione] has been used clinically and is of little toxicity. Comprehensive mechanistic and phase IIa clinical studies supported the notion that oltipraz exerts chemopreventive effects against chemical carcinogenesis. We report here that oltipraz within the clinical dose range regenerates cirrhotic liver in the established LC rats as a result of reduction of the intensities of cirrhotic nodules, elimination of accumulated extracellular matrix, and inactivation of stellate cells, thereby improving survival rate. We also reveal that activation of CCAAT/enhancer binding protein by oltipraz inhibits transforming growth factor b1 gene expression in stellate cells, which provides a molecular target for pharmacological treatment of LC. Oltipraz is the first therapeutic agent that regenerates cirrhotic liver.

Pharmacokinetics of theophylline in diabetes mellitus rats: induction of CYP1A2 and CYP2E1 on 1,3-dimethyluric acid formation.

Pharmacokinetic parameters of theophylline and one of its metabolites, 1,3-dimethyluric acid (1,3-DMU), were compared after intravenous and oral administration of aminophylline, 5mg/kg as theophylline, to diabetes mellitus rats induced by alloxan (DMIA) or streptozotocin (DMIS), and their respective control rats. In DMIA and DMIS rats, expression of CYP1A2 and 2E1 increased approximately three times. Theophylline was metabolized to 1,3-DMU by CYP1A2 and 2E1 in rats. Hence, it was expected that formation of 1,3-DMU increased in DMIA or DMIS rats. This was proven by the following results. First, after intravenous administration of theophylline, the AUC of 1,3-DMU was significantly greater in DMIA (110% increase) or DMIS (47.4% increase) rats. Second, the AUC of theophylline was significantly smaller in DMIA (26.1% decrease) or DMIS (30.1% decrease) rats because of significantly faster time-averaged total body clearance in DMIA (34.8% increase) or DMIS (42.7% increase) rats. Third, based on in vitro hepatic microsomal studies, intrinsic 1,3-DMU formation clearances were significantly faster in DMIA (20.4% increase) or DMIS (30.7% increase) rats than respective control rats. Similar results (AUC values of theophylline and 1,3-DMU) were also obtained after oral administration.

Effect of enzyme inducers and inhibitors on the pharmacokinetics of oltipraz in rats.

A series of in-vitro and in-vivo experiments, using various inducers and inhibitors of hepatic microsomal cytochrome P450 (CYP) isozymes, was conducted to study oltipraz pharmacokinetics in rats. In in-vivo studies, oltipraz at a dose of 10 mg kg(-) was administered intravenously to rats. In rats pretreated with SKF 525-A (a nonspecific CYP isozyme inhibitor in rats; n-9), the time-averaged total body clearance (CL) of oltipraz was significantly slower (56.6% decrease) than that in untreated rats (n=9). This indicated that oltipraz is metabolized via CYP isozymes in rats. Hence, various enzyme inducers or inhibitors were used in in-vitro and in-vivo studies in rats. In rats pretreated with 3-methylcholanthrene (n=9 and 8 for untreated and treated groups, respectively), phenobarbital (n=7 and 10 for untreated and treated groups, respectively) or dexamethasone (n=7 and 12 for untreated and treated groups, respectively) (main inducers of CYP1A1/2, 2B1/2 and 3A1/2 in rats, respectively), the CL values were significantly faster (38.4, 94.4 and 33.6% increase, respectively). In rats pretreated with sulfaphenazole (n=8 and 9 for untreated and treated groups, respectively), quinine (n=7 and 9 for untreated and treated groups, respectively) or troleandomycin (n=8 and 9 for untreated and treated groups, respectively) (main inhibitors of CYP2C11, 2D1 and 3A1/2 in rats, respectively), the CL values were significantly slower (31.0, 27.6 and 36.3% decrease, respectively). The in-vivo results with various enzyme inhibitors correlated well with the in-vitro intrinsic clearance for disappearance of oltipraz (CL(int)) (n=5, each). The above data suggested that oltipraz could be metabolized in male rats mainly via CYP1A1/2, 2B1/2, 2C11, 3A1/2 and 2D1.