A Randomized, Multi-Center, Open-Label Study to Evaluate the Efficacy of Carvedilol vs. Propranolol to Reduce Portal Pressure in Patients With Liver Cirrhosis.

OBJECTIVES: Propranolol has been used as prophylaxis for variceal bleeding in patients with cirrhosis. More recent data suggest that carvedilol may be more effective for reducing the hepatic venous pressure gradient (HVPG) than propranolol. The primary aim of this study was to evaluate the hemodynamic response to carvedilol compared with propranolol. METHODS: A total of 110 patients with a baseline HVPG value >12 mm Hg were allocated randomly to receive either carvedilol or propranolol. The HVPG measurement was repeated after 6 weeks of daily medication. The primary end point was a ≥20% fall in HVPG compared with baseline or <12 mm Hg. RESULTS: The difference in the proportion of responders in the carvedilol (49.1%) vs. propranolol (30.9%) groups did not reach statistical significance in the intention-to-treat analysis (P=0.08). However, among patients with a model for end-stage liver disease (MELD) score ≥15, carvedilol resulted in a significantly greater response than that of propranolol (7/12, 58.3% vs. 0/10, 0%; P=0.005). Similarly, carvedilol was superior to propranolol in patients with Child-Pugh score ≥9 (46.2 vs. 0%; P=0.046). The presence of ascites also had a significant influence on the response rate (51.5 vs. 24.2%; P=0.042). A MELD score ≥15 was the only significant predictor of response among these post hoc groups after adjusting for multiple comparisons (P=0.005). Severe adverse events were higher in the carvedilol group although drug-associated adverse events were not different. CONCLUSIONS: Overall, carvedilol offered no clear advantage over propranolol but it may be more effective in advanced cirrhotic patients with a MELD score≥15 in reducing the portal pressure gradient. However, this potential benefit may come with a cost of increased risk of side-effects and outcome data over a longer term is needed to understand the relative risk benefit.

Effects of E. Coli lipopolysaccharide on the pharmacokinetics of ipriflavone and its metabolites, M1 and M5, after intravenous and oral administration of ipriflavone to rats: decreased metabolism of ipriflavone due to decreased expression of hepatic CYP1A2 and 2C11.

It was reported that ipriflavone was primarily metabolized via hepatic CYP1A1/2 and 2C11 in rats. In the present study, the expression of CYP1A2 and 2C11 decreased in the liver, but increased in the intestine in rats pretreated with E. coli lipopolysaccharide (ECLPS; an animal model of inflammation). Thus, pharmacokinetic parameters of ipriflavone and its metabolites, M1 and M5, were evaluated in ECLPS rats. After intravenous administration (20 mg/kg) to ECLPS rats, the AUC of ipriflavone was significantly greater (26.7% increase) and CL(NR) of ipriflavone was significantly slower (19.9% decrease) than in the controls. This could have been due to decreased expression of hepatic CYP1A2 and 2C11 compared to the controls. After oral administration (200 mg/kg) to ECLPS rats, the AUC of ipriflavone was also significantly greater (130% increase) than in the controls. Although the expression of intestinal CYP1A2 and 2C11 increased in ECLPS rats, contribution of this increase to the significantly greater AUC of ipriflavone after oral administration of ipriflavone to ECLPS rats was not considerable. This could have also been due to a significantly decreased expression of hepatic CYP1A2 and 2C11 in ECLPS rats. The formation of M1 and M5 could be mediated via CYP1A2 and/or 2C11 in rats.

Predictive factors for lymph node metastasis and endoscopic treatment strategies for undifferentiated early gastric cancer.

BACKGROUND AND AIM: Although more than 80% of undifferentiated early gastric cancers (EGC) are not associated with lymph node metastasis, endoscopic mucosal resection is not generally accepted as a means of curative treatment because of an abundance of conflicting data concerning clinicopathological characteristics and prognoses. The aim of this study was to define a subgroup of undifferentiated EGC that could be cured by endoscopic treatment without the risk of lymph node metastasis. METHOD: A total of 591 patients surgically resected for undifferentiated EGC between January 1999 and March 2005 were reviewed. Associations between various clinicopathological factors and the presence of lymph node metastasis were analyzed to identify the risk factors of lymph node metastasis. RESULTS: Lymph node metastasis was found in 79 patients (13.4%). By multivariate logistic regression analysis, a tumor diameter 2.5 cm or larger, invasion into the middle third of the submucosal layer or deeper, and lymphatic involvement were identified as independent risk factors of lymph node metastasis (P < 0.001, respectively). Lymph node metastasis was not found in any patient with undifferentiated EGC smaller than 2.5 cm confined to the mucosa or upper third of the submucosal layer without lymphatic involvement. CONCLUSIONS: Undifferentiated intramucosal EGC smaller than 2.5 cm without lymphatic involvement was not associated with lymph node metastasis. Thus, we propose in this circumstance that endoscopic mucosal resection could be considered a definitive treatment without compromising the possibility of cure.

Dose-independent pharmacokinetics of metformin in rats: Hepatic and gastrointestinal first-pass effects.

Pharmacokinetic parameters of metformin were evaluated after intravenous and oral administration (50, 100, and 200 mg/kg) in rats. The hepatic, gastric, and intestinal first-pass effects were also measured after intravenous, intraportal, intragastric, and intraduodenal administration (100 mg/kg) in rats. The total area under the plasma concentration-time curve from time zero to time infinity (AUC) values were dose-proportional after both intravenous and oral dose ranges studied. After oral administration (100 mg/kg), approximately 4.39% of oral dose was not absorbed and extent of absolute oral bioavailability (F) value was approximately 29.9%. The gastrointestinal first-pass effect of metformin was approximately 53.8% of oral dose in rats (the gastric and intestinal first-pass effects were approximately 23.1 and 30.7%, respectively), and the hepatic first-pass effect was approximately 27.1% after absorption into the portal vein. Since approximately 41.8% of oral metformin was absorbed into the portal vein, the value of 27.1% is equivalent to 11.3% of oral dose. The first-pass effects of metformin in the lung and heart were almost negligible in rats. The low F value of metformin in rats was mainly due to considerable gastrointestinal first-pass effects. The stability of metformin, distribution of metformin between plasma and blood cells, and factors affecting protein binding of metformin to 4% human serum albumin were also discussed.

Pharmacokinetics and therapeutic effects of oltipraz after consecutive or intermittent oral administration in rats with liver cirrhosis induced by dimethylnitrosamine.

Pharmacokinetics and therapeutic effects of oltipraz were evaluated after consecutive (once per day at 30 mg/kg/day for 7 and 14 days) or intermittent (once per week at 100 mg/kg/week for 1-3 weeks) oral administration to rats with liver cirrhosis induced by dimethylnitrosamine. The AUC of oltipraz was significantly greater in cirrhotic rats than controls (890 compared with 270 microg . min/mL) due to impaired liver function in cirrhotic rats. However, the AUC values after consecutive 7 (421 compared with 753 microg . min/mL) and 14 (309 compared with 821 microg . min/mL) days oral administration of oltipraz in cirrhotic rats were significantly smaller than those in respective vehicle-treated cirrhotic rats. Moreover, the AUC values after intermittent 2 and 3 weeks in cirrhotic rats were also significantly smaller than that in 1 week vehicle-treated cirrhotic rats (2370 and 1690 compared with 4760 microg . min/mL). This could be due to induction of CYP isozymes and considerably greater numbers of normal liver cells in cirrhotic rats by oral administration of oltipraz. Improved liver function by oltipraz in cirrhotic rats was proved by liver microscopy; livers are free of significant fibrosis, although evidence of bridging necrosis is still present in many rats.

Hepatic and intestinal first-pass effects of oltipraz in rats.

It was reported that the mean value of the extent of absolute oral bioavailability (F) of oltipraz at a dose of 20 mg/kg was 41.2% and only 2.68% of the oral dose was unabsorbed from the gastrointestinal tract in rats. Hence, the low F in rats could be due to considerable first-pass (gastric, intestinal and hepatic) effects. Hence, the first-pass effects of oltipraz were measured after intravenous, intraportal, intragastric and intraduodenal administration of the drug at a dose of 20 mg/kg to rats. The total area under the plasma concentration-time curve from time zero to time infinity (AUC) values between intragastric and intraduodenal administration (213 and 212 microg min/ml) in rats were almost similar, but the values were significantly smaller than that after intraportal administration (316 microg min/ml) in rats, indicating that gastric first-pass effect was almost negligible (due to negligible absorption of oltipraz from rat stomach), but the intestinal first-pass effect of oltipraz was considerable, approximately 32% of the oral dose. The hepatic first-pass effect of oltipraz was approximately 40% based on AUC values between intravenous and intraportal administration (319 versus 536 microg min/ml). Since approximately 65% of the oral oltipraz was absorbed into the portal vein, the value of 40% was equivalent to 25% of the oral dose. The low F of oltipraz in rats was mainly due to considerable hepatic and intestinal first-pass effects.

Effects of activated carbon types and service life on removal of endocrine disrupting chemicals: amitrol, nonylphenol, and bisphenol-A.

Removal performances of endocrine disrupting chemicals (EDC) such as amitrol, nonylphenol, and bisphenol-A were evaluated in this study using granular activated carbon (GAC) adsorption. This study found that GAC adsorption was effective in removal of EDCs with high K(ow) value. Nonylphenol and bisphenol-A were effectively adsorbed onto all carbons (including the used carbons) tested in this study. As indicated by K(ow) value, nonylphenol was more effectively adsorbed than bisphenol-A. The coal-based carbon was found more effective than other carbons in the adsorption of nonylphenol and bisphenol-A due to its larger pore volume. The adsorption capacity reduced with the operation year, and the extent of the reduction was different depending upon the carbon type and the operation year. Amitrol was effectively removed by biological degradation, but was poorly adsorbed. Since the microbes residing at the used carbons already accustomed to amitrol, the used carbons removed amitrol better than the virgin carbons. Although the coal-based carbon showed the best removal performance of amitrol, GAC adsorption could not be recommended for amitrol removal because considerable portion of incoming amitrol (9-87%) passed through GAC adsorption column. According to this study, pore volume mainly influenced the adsorption capacity, but the surface charge was also important due to electrical interaction. The adsorption parameters for nonylphenol and bisphenol-A provided by this study could be valuable when GAC adsorption was considered to handle an accidental spill of nonylphenol and bisphenol-A.

Pharmacokinetics of oltipraz after intravenous and oral administration in rats with dehydration for 72 hours.

Pharmacokinetic parameters of oltipraz were compared after intravenous and oral administration at a dose of 30 mg/kg to control rats and rats with water deprivation for 72 h (rats with dehydration). The plasma protein binding of oltipraz was measured in both groups of rats using an equilibrium dialysis technique. The concentrations of oltipraz were measured by the reported HPLC analysis. After intravenous administration, the total area under the plasma concentration-time curve from time zero to time infinity (AUC), terminal half-life, time-averaged total body and nonrenal clearances, and apparent volume of distribution at steady state were not significantly different between the two groups of rats. However, after oral administration to rats with dehydration, the AUC was significantly smaller than that in control rats (180 versus 316 microg min/ml) mainly due to decrease in absorption. In rats with dehydration, plasma protein binding was significantly greater than that in control rats (91.5 +/- 0.309 versus 81.3 +/- 2.79%).

Pharmacokinetics of clarithromycin in rats with acute renal failure induced by uranyl nitrate.

In rats pretreated with dexamethasone (an inducer of CYP3A1/2 in rats) and troleandomycin (an inhibitor of CYP3A1/2 in rats), the area under the plasma concentration-time curve from time zero to time infinity (AUC) values of clarithromycin were significantly smaller (365 compared with 600 micro g min/ml) and greater (1410 compared with 581 micro g min/ml), respectively, than those in control rats. This indicated that clarithromycin was metabolized via CYP3A1/2 in rats. The expression of CYP3A1(23) increased in rats with acute renal failure induced by uranyl nitrate (rats with U-ARF). Hence, it could be expected that AUC of clarithromycin could be smaller in rats with U-ARF. However, after intravenous administration of clarithromycin at a dose of 20mg/kg, the AUC and time-averaged total body (Cl) and nonrenal (Cl(nr)) clearance values were comparable between the two groups of rats. The 9000 x g supernatant fraction of liver homogenates in rats with U-ARF had comparable metabolic activities for clarithromycin compared with those in control rats, suggesting that the CYP3A isozyme responsible for metabolism of clarithromycin seemed not to be expressed considerably in the rats. This could explain the comparable AUC, Cl and Cl(nr) values of clarithromycin between the two groups of rats.

Effects of acute renal failure on the pharmacokinetics of oltipraz in rats.

Pharmacokinetic parameters of oltipraz were compared after intravenous and oral administration at a dose of 30 mg/kg to control rats and rats with U-ARF. After intravenous administration to rats with U-ARF, the AUC was significantly greater (1100 versus 1730 microg x min/mL) than that in control rats, and this could be due to significantly slower CL (27.2 versus 17.3 mL/min/kg). The slower CL could be mainly due to significantly slower CL(NR) (27.2 versus 17.3 mL/min/kg), and this could be supported by significantly slower in vitro CL(int) (32.1 versus 13.2 mL/min/whole liver) in the rats. The Vss was significantly larger in rats with U-ARF (4050 versus 5680 mL/kg), and this was not due to a significant increase in free fractions (unbound in plasma proteins) of oltipraz in the rats because the free fractions were 17.0 and 15.7% for control rats and rats with U-ARF, respectively. Unexpectedly, after oral administration to rats with U-ARF, the AUC of oltipraz was significantly smaller than that in control rats (329 versus 149 microg x min/mL), and this could be mainly due to a decrease in the absorption of oltipraz from the gastrointestinal tract in the rats (95 and 72% of the oral dose were absorbed in control rats and rats with U-ARF, respectively).

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

Effects of cysteine on the pharmacokinetics of torasemide were investigated after intravenous administration at a dose of 2 mg/kg to control rats and rats with PCM and PCMC. Torasemide was reported to be mainly metabolized via hepatic CYP2C9 in humans, and human CYP2C9 and male rat CYP2C11 proteins have 77% homology. It has also been reported that in male rats with PCM, the CYP2C11 level decreased to approximately 20% of the control level, but the decreased CYP2C11 level in rats with PCM partially returned to the control level by oral cysteine supplementation (rats with PCMC). Hence, it could be expected that in rats with PCM, some pharmacokinetic parameters of torasemide could be significantly different compared with those in control rats and rats with PCMC; however, they could be not significantly different between control rats and rats with PCMC. This was proven by the following parameters; the AUC (1880, 4080, and 2290 microg x min/mL for control rats and rats with PCM and PCMC, respectively), terminal half-life (188, 277, and 139 min), MRT (154, 323, and 155 min), CL (1.06, 0.491, and 0.943 mL/min/kg), CL(NR) (0.992, 0.430, and 0.874 mL/min/kg), and in vitro intrinsic torasemide disappearance clearance, CL(int) (0.102, 0.0842, and 0.0997 mL/min/mg protein).

Pharmacokinetic changes of oltipraz after intravenous and oral administration to rats with liver cirrhosis induced by dimethylnitrosamine.

Pharmacokinetic changes of oltipraz were investigated after intravenous and oral administration at a dose of 30 mg/kg to control Sprague-Dawley rats and rats with liver cirrhosis induced by dimethylnitrosamine. After intravenous administration in rats with liver cirrhosis, the area under the plasma concentration-time curve from time zero to time infinity (AUC) was significantly greater (1490 microg min/ml versus 2840 microg min/ml) than that in control rats. This was due to significantly slower total body clearance (CL) (20.2 ml/(min kg) versus 10.6 ml/(min kg)) in the rats. The slower CL was due to significantly slower CL(NR) (20.1 ml/(min kg) versus 10.5 ml/(min kg)) in rats with liver cirrhosis. The significantly slow CL(NR) was due to slower hepatic blood flow rate and significantly slower in vitro intrinsic oltipraz disappearance clearance (CL(int), 77.2 ml/min per whole liver versus 11.5 ml/min per whole liver) because the free (unbound in serum proteins) fraction of oltipraz was significantly greater (15.1% versus 31.3%) in the rats. After oral administration in rats with liver cirrhosis, the AUC was also significantly greater (354 microg min/ml versus 812 microg min/ml) and this was not due to increased absorption in the rats. This also could be due to slower hepatic blood flow rate and significantly slower CL(int) in the rats.

Effects of acute renal failure induced by uranyl nitrate on the pharmacokinetics of 2-(allylthio) pyrazine, a chemoprotective agent, in rats: the role of CYP3A23 induction.

It has been reported that the total body clearance (CL) of 2-(allylthio)pyrazine (2-AP) was significantly faster after intravenous administration of 2-AP to rats pretreated with 3-methylcholanthrene, phenobarbital, and dexamethasone (main inducers of CYP1A1/2, CYP2B1/2, and CYP3A1/2, respectively, in rats) than those in respective control rats. It has also been reported that expression of CYP2E1 and CYP3A1(23) increased 2.3 and 4 times, respectively, in rats with acute renal failure induced by uranyl nitrate (U-ARF) compared with those in control rats. However, CYP1A2 and CYP2B1/2 expression was not changed. Therefore, it could be expected that the pharmacokinetics of 2-AP could be changed in rats with U-ARF due to increase in expression of CYP3A23 in the rats. After intravenous administration of 2-AP at a dose of 50 mg/kg to rats with U-ARF, the area under the plasma concentration-time curve from time zero to time infinity of 2-AP was significantly smaller (1030 versus 1360 microg min/ml) due to significantly faster CL of 2-AP (48.4 versus 36.8 ml/min/kg). This could be due to increased expression of CYP3A23 in rats with U-ARF.

Insulin and glucagon signaling in regulation of microsomal epoxide hydrolase expression in primary cultured rat hepatocytes.

Microsomal epoxide hydrolase (mEH) plays an important role in the detoxification of a broad range of epoxide intermediates and has been reported to be decreased during diabetes and fasting. The signaling pathways involved in the regulation of mEH expression in response to insulin and glucagon were examined in primary cultured rat hepatocytes. mEH protein levels were increased 2- to 6-fold in hepatocytes cultured for 1 to 4 days, respectively, in the presence of insulin. Concentration-response studies revealed that insulin concentrations >or=1 nM resulted in increased mEH protein levels. The phosphatidylinositol 3-kinase (PI3K) inhibitors wortmannin or LY294002 [2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one], and rapamycin, an inhibitor of p70 S6 kinase phosphorylation, ameliorated the insulin-mediated increase in mEH protein levels. The p38 mitogen-activated protein (MAP) kinase inhibitors SB203580 and SB202190 also abrogated the insulin-mediated increase in mEH protein. Treatment of cells with glucagon, 8-bromo-cAMP, or dibutyryl-cAMP for 3 days resulted in decreased mEH protein levels. Pretreatment with the protein kinase A (PKA) inhibitor H89 (N-[2-(4-bromocinnamylamino)ethyl]-5-isoquinoline) prior to glucagon addition markedly attenuated the glucagon effect, implicating PKA signaling in the regulation of mEH expression. These data demonstrate that insulin and glucagon regulate, in an opposing manner, the expression of mEH in primary cultured rat hepatocytes. Furthermore, these data suggest that PI3K and p70 S6 kinase are active in the regulation of insulin-mediated mEH expression. We also provide data implicating p38 MAP kinase in the insulin-mediated increase in mEH levels. Moreover, cAMP and PKA are implicated in mediating the inhibitory effect of glucagon on mEH expression.

Effects of glucose on the pharmacokinetics of intravenous chlorzoxazone in rats with acute renal failure induced by uranyl nitrate.

The effects of glucose on CYP2E1 expression in rats with acute renal failure induced by uranyl nitrate (U-ARF) have been reported. CYP2E1 was significantly induced (2.3-fold) in rats with U-ARF compared with that in control rats. In contrast, CYP2E1 expression was significantly decreased in rats with U-ARF supplied with glucose (dissolved in tap water to make 10%, w/v) in their drinking water for 5 days (U-ARFG) compared with that in rats with U-ARF. However, CYP2E1 in rats with U-ARFG was significantly greater than that in control rats. Chlorzoxazone (CZX) primarily undergoes hydroxylation, catalyzed mainly by CYP2E1, to form 6-hydroxychlorzoxazone (OH-CZX) rats. Hence, it could be expected that in rats with U-ARFG, formation of OH-CZX could significantly decrease and increase compared with those in rats with U-ARF and control rats, respectively. This expectation is proven by the following results of a study of intravenous administration of CZX at a dose 20 mg/kg to control rats and rats with U-ARF and U-ARFG. First, the total area under the plasma concentration-time curve from time zero to 8 h (AUC(0-8 h)) of OH-CZX in rats with U-ARFG (8730 microg x min/mL) was significantly greater than that in control rats (414 microg x min/mL) and significantly smaller than that in rats with U-ARF (11500 microg x min/mL). Second, the AUC(0-8 h, OH-CZX)/AUC(CZX) ratio in rats with U-ARFG (10.0) was significantly greater than that in control rats (0.252) and significantly smaller than that in rats with U-ARF (17.5). Finally, the in vitro intrinsic OH-CZX formation clearance (CL(int)) in rats with U-ARFG (27.9 mL/min/mg protein) was significantly slower than that in rats with U-ARF (36.7 mL/min/mg protein) and significantly faster than that in control rats (17.7 mL/min/mg protein).

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

Effects of cysteine on the pharmacokinetics of clarithromycin were investigated after intravenous administration of the drug at a dose of 20 mg/kg to control rats (4-week fed on 23% casein diet) and rats with PCM (protein-calorie malnutrition, 4-week fed on 5% casein diet) and PCMC (PCM treated with 250 mg/kg for oral cysteine twice daily during the fourth week). Clarithromycin has been reported to be metabolized via hepatic microsomal cytochrome P450 (CYP) 3A4 to 14-hydroxyclarithromycin (primary metabolite of clarithromycin) in human subjects. It has also been reported that in rats with PCM, CYP3A23 level decreased to 40-50% of control level, but decreased CYP3A23 level in rats with PCM completely returned to control level by oral cysteine supplementation (rats with PCMC). Human CYP3A4 and rat CYP3A23 proteins have 73% homology. In rats with PCM, the area under the plasma concentration-time curve from time zero to time infinity, AUC (567, 853 and 558 microg min/ml for control rats and rats with PCM and PCMC, respectively) and percentage of clarithromycin remaining after incubation with liver homogenate (69.6, 83.9 and 71.7%) were significantly greater than those in control rats and rats with PCMC. Moreover, in rats with PCM, the total body clearance, CL (35.3, 23.4 and 35.8 ml/min/kg), nonrenal clearance, CL(NR) (21.3, 15.2 and 24.1 ml/min/kg) and maximum velocity for the disappearance of clarithromycin after incubation with hepatic microsomal fraction, V(max) (351, 211 and 372 pmol/min/mg protein) were significantly slower than those in control rats and rats with PCMC. However, above mentioned each parameter was not significantly different between control rats and rats with PCMC. The above data suggested that metabolism of clarithromycin decreased significantly in rats with PCM as compared to control due to significantly decreased level of CYP3A23 in the rats. By cysteine supplementation (rats with PCMC), some pharmacokinetic parameters of clarithromycin (AUC, CL, CL(NR) and V(max)) were restored fully to control levels because CYP3A23 level was completely returned to control level in rats with PCMC.

Pharmacokinetics of intravenous chlorzoxazone in rats with dehydration and rehydration: effects of food intakes.

The following results were obtained recently from our laboratories; in rats with 72-h water deprivation (rats with dehydration), the hepatic cytochrome P450 2E1 (CYP2E1) was three-fold induced with an increase in the mRNA. Rehydration of 48-h water-deprived rats for the next 24 h with free access of food (rats with rehydration) restored CYP2E1 level to that of control. However, rehydration of 48-h water-deprived rats for the next 24 h with limited food supply (20% of control) failed to restore the CYP2E1 level to that of control. Hence, the CYP2E1 changes in rats with dehydration and rehydration resulted from differences in food intakes but not from dehydration or rehydration per'se. Chlorzoxazone (CZX) is metabolized to 6-hydroxychlorzoxazone (OH-CZX) mainly by CYP2E1 in rats. Therefore, the pharmacokinetics of CZX and OH-CZX were compared after intravenous administration of CZX, 25 mg/kg, to control rats and rats with dehydration and rehydration with free access of food. In rats with dehydration, the amount of 24-h urinary excretion of free OH-CZX plus its glucuronide conjugates (Ae (OH-CZX, 0-24 h,) expressed in terms of intravenous dose of CZX) was significantly greater (45.6 compared with 35.6%) and area under the plasma concentration-time curve from time zero to time infinity (AUC) of CZX was significantly smaller (2190 compared with 3200 micro g min/ml) than those in control rats. The above data indicated that the formation of OH-CZX increased significantly in rats with dehydration due to 3-fold induction of CYP2E1. In rats with rehydration with free access of food, the Ae (OH-CZX, 0-24 h) (39.0 compared with 35.6%) and AUC of CZX (2870 compared with 3200 micro g min/ml) were restored (comparable) to control levels since the expression of CYP2E1 in rats with dehydration returned to control level by rehydration. The above data indicate that CZX could be used as a chemical probe to assess the activity of CYP2E1 in rats with dehydration and rehydration.

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

The effects of cysteine on the pharmacokinetics of itraconazole were investigated after intravenous, 20 mg/kg, and oral, 50 mg/kg, administration of the drug to control rats (fed for 4 weeks on 23% casein diet) and rats with PCM (protein-calorie malnutrition, fed for 4 weeks on 5% casein diet) and PCMC (PCM with oral cysteine supplementation, 250 mg/kg, twice daily during the fourth week). After intravenous administration of itraconazole to rats with PCM, the area under the plasma concentration-time curve from time zero to time infinity (AUC) of itraconazole was significantly greater (3580 compared with 2670 and 2980 microg min/ml) than those in control rats and rats with PCMC (the values between control rats and rats with PCMC were not significantly different). The above data suggested that metabolism of itraconazole decreased significantly in rats with PCM due to suppression of hepatic microsomal cytochrome p450 (CYP) 3A23 in the rats. The results could be expected since in rats with PCM, the level of CYP3A23 decreased significantly as compared to control. Itraconazole was reported to be metabolized via CYP3A4 to several metabolites, including hydroxyitraconazole, in human subjects. Human CYP3A4 and rat CYP3A1 (CYP3A23) proteins have 73% homology. By cysteine supplementation (rats with PCMC), the AUC of itraconazole was restored fully to control levels.

Pharmacokinetics and pharmacodynamics of intravenous azosemide in mutant Nagase analbuminemic rats.

This paper reports 1) the increase in expression of CYP1A2 in mutant Nagase analbuminemic rats (NARs), 2) the role of globulin binding of azosemide in circulating blood in its urinary excretion and hence its diuretic effects in NARs, and 3) the significantly faster renal (CL(R)) and nonrenal (CL(NR)) clearances of azosemide in NARs. Azosemide (mainly metabolized via CYP1A2 in rats), 10 mg/kg, was intravenously administered to control rats and NARs. Northern and Western blot analyses revealed that the expression of CYP1A2 increased approximately 3.5-fold in NARs as compared with control. The plasma protein binding of azosemide in control rats and NARs was 97.9 and 84.6%, respectively. In NARs, plasma protein binding (84.6%) was due to binding to alpha- (82.6%) and beta- (68.9%) globulins. In NARs, the amount of unchanged azosemide excreted in 8-h urine was significantly greater (37.7 versus 21.0% of intravenous dose) than that in control rats due to an increase in intrinsic renal active secretion of azosemide. Accordingly, the 8-h urine output was significantly greater in NARs. The area under the plasma concentration-time curve of azosemide was significantly smaller (505 versus 2790 microg. min/ml) in NARs because of markedly faster CL(R) (7.36 versus 0.772 ml/min/kg, secondary to a significant increase in urinary excretion of azosemide and intrinsic renal active secretion). Additionally, CL(NR) was significantly faster (12.4 versus 3.05 ml/min/kg, because of approximately 3.5 fold increase in CYP1A2) in NARs compared with control. Based on in vitro hepatic microsomal studies, the intrinsic M1 [a metabolite of azosemide; 5-(2-amino-4-chloro-5-sulfamoylphenyl)-tetrazole] formation clearance was significantly faster (67.0% increase) in NARs than that in control rats, and this supports significantly faster CL(NR) in NARs. Renal sensitivity to azosemide was significantly greater in NARs than in control rats with respect to 8-h urine output (385 versus 221 ml/kg) and 8-h urinary excretions of sodium, potassium, and chloride. This study supports that in NARs, binding of azosemide to alpha- and beta-globulins in circulating blood play an important role in its diuretic effects.