Faster clearance of omeprazole in rats with acute renal failure induced by uranyl nitrate: contribution of increased expression of hepatic cytochrome P450 (CYP) 3A1 and intestinal CYP1A and 3A subfamilies

It has been reported that omeprazole is mainly metabolized via hepatic cytochrome P450 (CYP) 1A1/2, CYP2D1 and CYP3A1/2 in male Sprague-Dawley rats, and the expression of hepatic CYP3A1 is increased in male Sprague-Dawley rats with acute renal failure induced by uranyl nitrate (U-ARF rats). Thus, the metabolism of omeprazole would be expected to increase in U-ARF rats. After intravenous administration of omeprazole (20 mgkg(-1)) to U-ARF rats, the area under the plasma concentration-time curve from time zero to infinity (AUC) was significantly reduced (371 vs 494 microg min mL(-1)), possibly due to the significantly faster non-renal clearance (56.6 vs 41.2 mL min(-1) kg(-1)) compared with control rats. This could have been due to increased expression of hepatic CYP3A1 in U-ARF rats. After oral administration of omeprazole (40 mgkg(-1)) to U-ARF rats, the AUC was also significantly reduced (89.3 vs 235 microg min mL(-1)) compared with control rats. The AUC difference after oral administration (62.0% decrease) was greater than that after intravenous administration (24.9% decrease). This may have been primarily due to increased intestinal metabolism of omeprazole caused by increased expression of intestinal CYP1A and 3A subfamilies in U-ARF rats, in addition to increased hepatic metabolism.     

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.     

Slower clearance of intravenous metformin in rats with acute renal failure induced by uranyl nitrate: Contribution of slower renal and non-renal clearances

It has been reported that metformin was primarily metabolized via hepatic CYP2C11, 2D1, and 3A1/2 in rats. It has also been reported that the protein expression and/or mRNA levels of hepatic CYP2C11, 2D subfamily, and 3A1 have decreased, decreased, and increased, respectively, in U-ARF rats. Thus, pharmacokinetic changes of intravenous metformin in U-ARF rats were evaluated. Metformin was administered intravenously at a dose of 50 mg/kg to control and U-ARF rats. After i.v. administration of metformin to U-ARF rats, its time-averaged total body clearance was significantly slower (95.2% decrease) than controls. This could have been due to both significantly slower time-averaged renal clearance (99.1% decrease; due to a urine flow rate-dependent timed-interval renal clearance of the drug, a decrease in renal OCT2, and/or an impaired kidney function in U-ARF rats) and time-averaged non-renal clearance (83.8% decrease; due to a decrease in hepatic CYP2C11 and 2D subfamily in U-ARF rats).     

Faster clearance of omeprazole in mutant Nagase analbuminemic rats: possible roles of increased protein expression of hepatic CYP1A2 and lower plasma protein binding

It is well known that there are various changes in the expression of hepatic and intestinal CYPs in mutant Nagase analbuminemic rats (NARs). It has been reported that the protein expression of hepatic CYP1A2 was increased, whereas that of hepatic CYP3A1 was not altered, and it was also found that the protein expression of the intestinal CYP1A subfamily significantly increased in NARs from our other study. In addition, in this study additional information about CYP changes in NARs was obtained; the protein expression of the hepatic CYP2D subfamily was not altered, but that of the intestinal CYP3A subfamily increased in NARs. Because omeprazole is metabolized via hepatic CYP1A1/2, 2D1, 3A1/2 in rats, it could be expected that the pharmacokinetics of omeprazole would be altered in NARs. After intravenous administration of omeprazole to NARs, the Cl_nr was significantly faster than in the controls (110 versus 46.6 ml/min/kg), and this could be due to an increase in hepatic metabolism caused by a greater hepatic CYP1A2 level in addition to greater free fractions of the drug in NARs. After oral administration of omeprazole to NARs, the AUC was also significantly smaller (80.1% decrease) and F was decreased in NARs. This could be primarily due to increased hepatic and intestinal metabolism caused by greater hepatic CYP1A2 and intestinal CYP1A and 3A levels. In particular, the smaller F could mainly result from greater hepatic and intestinal first‐pass effect in NARs than in the controls. Copyright © 2009 John Wiley & Sons, Ltd.     

Pharmacokinetic changes of ipriflavone in rats with acute renal failure induced by uranyl nitrate

Pharmacokinetic parameters of ipriflavone were compared after intravenous (20 mg/kg) and oral (200 mg/kg) administration in control rats and in rats with acute renal failure induced by uranyl nitrate (U-ARF rats). It was expected that the time-averaged nonrenal clearance (Cl(nr)) of ipriflavone in U-ARF rats could be significantly slower than in the control rats, since it was reported that ipriflavone was metabolized via the hepatic microsomal cytochrome P450 (CYP) 1A1/2 and 2C11 and the expression and mRNA level of CYP1A2 were not changed, but those of CYP2C11 were decreased in U-ARF rats compared with control rats. Unexpectedly, after intravenous administration in U-ARF rats, the Cl(nr) of ipriflavone was significantly faster than in the controls (40.8 compared with 29.0 ml/min/kg). This may be due to an increase in the glucuronide conjugate formation of ipriflavone metabolites in U-ARF rats. After oral administration of ipriflavone in U-ARF rats, the AUC(0-24 h) was significantly smaller (194 compared with 295 microg min/ml) than in the controls.     

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 acute renal failure induced by uranyl nitrate on the pharmacokinetics of intravenous theophylline in rats: the role of CYP2E1 induction in 1,3-dimethyluric acid formation

In rats with acute renal failure induced by uranyl nitrate, the hepatic microsomal cytochrome P450 (CYP) 2E1 and CYP3A23 increased 2-4- and 4-times, respectively, CYP2C11 decreased to 80% of control, but the levels of CYP1A2 and CYP2B1/2 were not changed. It has been reported that theophylline was metabolized to 1,3-dimethyluric acid by CYP1A2 and CYP2E1 and 1-methylxanthine via CYP1A2, which was metabolized further to 1-methyluric acid via xanthine oxidase in rats. Hence, it was expected that the formation of 1,3-dimethyluric acid would show an increase in rats with renal failure as a result of induction of CYP2E1. The pharmacokinetics of theophylline were compared in control rats and rats with renal failure after intravenous administration of aminophylline, 5 mg kg(-1) as theophylline. In rats with renal failure, the plasma concentrations of theophylline were considerably lower and the resultant total area under the plasma concentration-time curve from time zero to time infinity (AUC(0- infinity )) of theophylline was significantly smaller (2,200 vs 1,550 microg min mL(-1)) compared with control rats. In rats with renal failure, the plasma concentrations of 1,3-dimethyluric acid were considerably higher and the resultant AUC(0-6 h) of 1,3-dimethyluric acid was significantly greater (44.4 vs 456 microg min mL(-1)) compared with control rats. Moreover, the AUC(0-6 h, 1,3-dimethyluric acid)/AUC(0- infinity, theophylline) ratio increased from 2.02% in control rats to 29.4% in rats with renal failure. The in-vitro intrinsic 1,3-dimethyluric acid formation clearance was significantly faster in rats with renal failure (734 vs 529 10(-6) mL min(-1)) compared with control rats using hepatic microsomal fraction. The results led us to conclude that in rats with uranyl nitrate-induced renal failure after the administration of aminophylline, 5 mg kg(-1) as theophylline, there was an increase in the formation of 1,3-dimethyluric acid as a result of an increase in CYP2E1 expression.     

Effects of acute renal failure induced by uranyl nitrate on the pharmacokinetics of liquiritigenin and its two glucuronides, M1 and M2, in rats

Objectives Liver disease and acute renal failure (ARF) are closely associated. The pharmacokinetics of liquiritigenin (LQ), a candidate therapy for inflammatory liver disease, and its metabolites M1 and M2 were evaluated in rats with ARF induced by uranyl nitrate (U‐ARF rats). Methods LQ was administered intravenously (20 mg/kg) or orally (50 mg/kg) in U‐ARF and control rats, and uridine diphosphate‐glucuronosyltransferases (UGT) activity and uridine 5′‐diphosphoglucuronic acid (UDPGA) concentrations were determined in the liver and intestine. Key findings After intravenous LQ administration, U‐ARF rats displayed significantly slower LQ renal clearance but no significant changes in the LQ area under the plasma concentration–time curve (AUC) compared with controls. This was because of similar hepatic UGT activity and UDPGA levels between two groups, which resulted in comparable non‐renal clearance, as well as the limited contribution of LQ renal clearance to total LQ clearance. However, the AUC and AUC_M/AUC_LQ ratios of M1 and M2 were significantly increased in U‐ARF rats because of decreased urinary excretion of M1 and M2. Similar results were observed following oral administration because of the comparable LQ intestinal metabolism in both groups and decreased urinary excretion of M1 and M2 in U‐ARF rats. Conclusions U‐ARF rats displayed decreased urinary excretion of LQ glucuronides, resulting in significantly greater AUC and metabolite ratios of M1 and M2 following LQ administration.     

Comparative study on altered hepatic metabolism of CYP3A substrates in rats with glycerol-induced acute renal failure

To examine the mechanism accounting for the diverse alteration of hepatic metabolism of CYP3A substrates observed with renal function being severely impaired, the hepatic drug metabolizing activity was evaluated using liver microsomes prepared from rats with glycerol-induced acute renal failure (ARF). Midazolam, nifedipine and rifabutin were employed as representative CYP3A substrates. When the Michaelis-Menten parameters, K(m) and V(max) , were examined in the incubation study, the K(m) values of midazolam and nifedipine in ARF rats were shown to decrease by 50.9% and 29.9% compared with the normal value, respectively. The V(max) values of midazolam and nifedipine in ARF rats also decreased by 49.3% and 28.0%, respectively, showing that their decreased K(m) values accompanied the decreased V(max) values. The parameters of nifedipine seemed to alter to a lesser extent than those of midazolam. As for rifabutin metabolism, the decrease in the K(m) value was observed in ARF rats, but it did not accompany the decrease in the V(max) value. Then, the hepatic expressions of the CYP3A subfamily were examined with western blotting using anti-CYP3A1 and anti-CYP3A2 antibodies. It was revealed that the hepatic expression of CYP3A2 decreased, while that of CYP3A1 was unaffected. Additionally, a band signal deduced to originate from CYP3A9 was clearly detected in ARF, but not in normal rats. Considering each substrate having different specificities for CYP3A subfamily member proteins, individual alterations of hepatic CYP3A subfamily expression seem to underlie the diverse alterations of hepatic metabolism of CYP3A substrates in ARF rats.     

Co-regulation of CYP3A4 and CYP3A5 and contribution to hepatic and intestinal midazolam metabolism

We recently demonstrated that a variant allele of CYP3A5 (CYP3A5*3) confers low CYP3A5 expression as a result of improper mRNA splicing. In this study, we further evaluated the regulation of CYP3A5 in liver and jejunal mucosa from white donors. For all tissues, high levels of CYP3A5 protein were strongly concordant with the presence of a wild-type allele of the CYP3A5 gene (CYP3A5*1). CYP3A5 represented greater than 50% of total CYP3A content in nearly all of the livers and jejuna that carried the CYP3A5*1 wild-type allele. Overall, CYP3A5 protein content accounted for 31% of the variability in hepatic midazolam hydroxylation activity. Improperly spliced mRNA (SV1-CYP3A5) was found only in tissues containing a CYP3A5*3 allele. Properly spliced CYP3A5 mRNA (wt-CYP3A5) was detected in all tissues, but the median wt-CYP3A5 mRNA was 4-fold higher in CYP3A5*1/*3 livers compared with CYP3A5*3/*3 livers. Differences in wt-CYP3A5 and CYP3A4 mRNA content explained 53 and 51% of the interliver variability in CYP3A5 and CYP3A4 content, respectively. Hepatic CYP3A4 and CYP3A5 contents were not correlated when all livers were compared. However, for CYP3A5*1/*3 livers, levels of the two proteins were strongly correlated (r = 0.93) as were wt-CYP3A5 and CYP3A4 mRNA (r = 0.76). These findings suggest that CYP3A4 and CYP3A5 genes share a common regulatory pathway for constitutive expression, possibly involving conserved elements in the 5'-flanking region.     

Differential expression of renal adenosine A(1) receptors induced by acute renal failure

The distribution of renal adenosine A(1) receptors was investigated in rats with glycerol- or mercuric chloride (HgCl(2))-induced acute renal failure. Receptors were localised by autoradiography using [(3)H]8-cyclopentyl-1,3-dipropylxanthine ([(3)H]DPCPX), a selective A(1) adenosine receptor antagonist. In saline-injected control animals, significant labelling with [(3)H]DPCPX was detected in glomeruli, the inner stripe of outer medulla, and the inner medulla. Sixteen hours following induction of glycerol-induced acute renal failure (ARF), a 34% increase in labelling in glomeruli was noted compared to saline-injected controls, and by 48 hr, glomerular labelling had increased by 200%. In addition, 48 hr following glycerol injection, significant labelling was now detected in the cortical labyrinth and medullary rays whilst, in the inner medulla, labelling had decreased by 34%. By contrast to glycerol-induced ARF, the only significant change noted 48 hr following induction of HgCl(2)-induced ARF was a 39% decrease in labelling in the inner medulla. It is concluded that glycerol-induced ARF results in differential expression of renal adenosine A(1) receptors with increased expression in the cortex and reduced expression in the inner medulla. Increased density of A(1) receptors in glomeruli may account, at least in part, for the increased renal vasoconstrictor response to adenosine and depressed glomerular filtration rate noted previously in this type of acute renal failure.     

Pharmacokinetic changes of DA-8159, a new erectogenic, after intravenous and oral administration to rats with acute renal failure induced by uranyl nitrate

The pharmacokinetic parameters of DA-8159, a new erectogenic, were compared after intravenous and oral administration of the drug at a dose of 30 mg/kg to control rats and rats with acute renal failure induced by uranyl nitrate (U-ARF). After intravenous administration to rats with U-ARF, the plasma concentrations of DA-8159 were higher than those in control rats. This resulted in a significantly greater area under the plasma concentration-time curve from time zero to time infinity (AUC) of DA-8159 in rats with U-ARF (304 compared with 365 microg min/ml for control rats and rats with U-ARF). The significantly greater AUC in rats with U-ARF was due to significantly slower total body clearance (Cl) of DA-8159 (98.6 compared with 82.2 ml/min/kg). The significantly slower Cl in rats with U-ARF was due to slower renal clearance (1.07 ml/min/kg compared with not calculable, due to impaired kidney function) and nonrenal clearance (97.5 compared with 82.2 ml/min/kg due to slower metabolism) than those in control rats. After oral administration of DA-8159 to rats with U-ARF, the AUC (122 compared with 172 microg min/ml) was significantly greater and Cl(R) was slower (3.47 ml/min/kg compared with not calculable) than those in control rats. The significantly greater AUC in rats with U-ARF could be due to slower Cl of DA-8159 in the rats.     

Serum aminotransferase activity as a predictor of clearance of drugs metabolized by CYP isoforms in rats with acute hepatic failure induced by carbon tetrachloride

The values of serum aminotransferase activity (AST) in untreated rats and rats with acute hepatic failure at 24h after an oral administration of CCl(4) (0.5 ml/kg) were 85+/-9 IU/l and 4260+/-620 IU/l (mean+/-S.D., n=6), respectively. The values of total clearance (CL(tot)) after intravenous administration of caffeine, tolbutamide, chlorzoxazone or lidocaine (as probe drugs for various CYP isoforms) to CCl(4)-treated rats were decreased to about 1/8, 1/3, 1/3 or 1/2 compared with those in untreated rats. Good correlations were observed between mRNA expression and enzyme activity of CYP2C11, CYP2E1, CYP3A2 and CYP1A2 in livers of rats given various doses of CCl(4). There was also a good negative correlation between serum AST activity and hepatic enzyme activity of each CYP. The serum AST activities corresponding to a 50% decrease of CYP2C 11, CYP2E1, CYP3A2 and CYP1A2 activities were about 710, 780, 1030 and 1300 IU/l, respectively. In conclusion, when the serum AST value in CCl(4)-treated rats reached about 4000 IU/l, the hepatic CYP activities were one-tenth or less of the control, although the degree of decrease of the CL(tot) values varied markedly. Nevertheless, the AST value appears to be a promising candidate for an indicator to predict appropriate dose modification of drugs for patients with acute hepatic failure.     

Pharmacokinetic changes of drugs in rat model of acute renal failure induced by uranyl nitrate: correlation between drug metabolism and hepatic microsomal cytochrome P450 isozymes

In male Sprague-Dawley rat model of acute renal failure induced by uranyl nitrate (rat model of U-ARF), the expression of CYP2C11 decreased by 20% of control, whereas that of CYP2E1 and 3A1(23) increased 2-4 and 4 times, respectively, as compared with controls. The expressions of CYPIA2 and 2B1/2 were not changed by U-ARF. The mRNA level of CYP2E1 increased 3 times and that of CYP2C11 decreased to 25% of controls. However, those of CYP1A2, 2B1, 2B2, and 3A2 were comparable to controls. These results of Northern blot analysis were consistent with those of Western blot analysis. Interestingly, however, the mRNA level of CYP3A23 did not increase in rat model of U-ARF. Hence, the induction of CYP3A23 expression by U-ARF may result from protein stabilization (i.e., a decrease in protein turnover). Hence, in this review, the changes in pharmacokinetics of drugs in rat model of U-ARF [especially the total area under the plasma concentration-time curve from time zero to time infinity (AUC) changes of metabolite(s)] reported from the literatures were tried to be explained in terms of CYP isozyme changes in rat model of U-ARF. Otherwise, the time-averaged nonrenal (Cl(nr)) or total body (Cl) clearance, or AUC of parent drugs were compared.     

Modulation of hepatic CYP2A1, CYP2C11, and CYP3A9 expression in adult rats by neonatal administration of tamoxifen.

To examine the effect of neonatal administration of tamoxifen on adult expression of hepatic cytochrome P-450 (CYP) enzymes and steroid 5alpha-reductase, male and female Sprague-Dawley rats were injected s.c. with tamoxifen (20 microg) or peanut oil (control) once daily at days 1 to 5 of age and sacrificed at 3 months of age. Neonatal tamoxifen treatment did not affect b.wt. or liver weight of adult male and female rats, but decreased testicular weight by approximately 40% in adult male rats. Neonatal administration of tamoxifen decreased hepatic microsomal testosterone 6beta- and 7alpha-hydroxylase activities in adult female rats whereas it did not alter steroid 5alpha-reductase activity. The same treatment increased testosterone 7alpha-hydroxylase activity, but did not affect testosterone 6beta-hydroxylase or steroid 5alpha-reductase activity in adult male rats. Immunoblot analysis indicated that neonatal tamoxifen treatment decreased CYP2C11 protein level by 26% and increased CYP2A1 protein content by 2.6-fold in adult male rats, whereas it had no effect on CYP3A or CYP2B protein expression. The reduction in the CYP3A-mediated testosterone 6beta-hydroxylase activity in adult female rats was accompanied by a decrease in CYP3A9 mRNA expression. Analysis of serum hormone levels indicated that neonatal exposure to tamoxifen resulted in a decrease in serum 17beta-estradiol concentration in adult female rats, whereas it did not alter serum testosterone concentration in adult male rats. In summary, treatment of neonatal rats with tamoxifen produced a long-lasting effect on hepatic CYP2A1, CYP2C11, and CYP3A9 expression in addition to testicular weight and serum 17beta-estradiol concentration.     

Function of multidrug resistance-associated protein 2 in acute hepatic failure rats

The function of multidrug resistance-associated protein 2 (Mrp2) in the intestine and liver, as well as intestinal Mrp2 expression, was analyzed in CCl(4)-induced acute hepatic failure rats with hyperbilirubinemia. The plasma level of bilirubin glucuronides, endogenous Mrp2-substrates, was 26 microM at 24 h after CCl(4) treatment. Mrp2 protein levels in jejunum decreased to 41% of control level. Mrp2-mediated efflux of 2,4-dinitrophenyl-S-glutathione (DNP-GSH), an Mrp2-substrate, in jejunum decreased to 31% of control in vitro, and was almost completely suppressed in vivo to the same level as that in the presence of probenecid, an Mrp2-inhibitor. Biliary excretion of DNP-GSH was suppressed to the same level as that inhibited by intravenous probenecid. The suppression of Mrp2 and the increased plasma bilirubin glucuronides recovered within 24 h thereafter. These results suggest that hyperbilirubinemia in disease states may be related to the systemic suppression of Mrp2 function.     

Reduced hepatic uptake of propranolol in rats with acute renal failure

The effect of acute renal failure (ARF) on the hepatic uptake and metabolism of propranolol was investigated in relation to the hepatic clearance of the drug. ARF was induced by the subcutaneous injection of uranyl nitrate to rats. The uptake rate of propranolol in the isolated perfused liver was determined by the multiple-indicator dilution method and was found to decrease from 43.6 +/- 2.0 min-1 (mean +/- S.E.) in control to 29.4 +/- 1.7 min-1 in ARF (P less than 0.001). The recovery fraction of propranolol in effluent venous blood increased about twofold in ARF compared to control (P less than 0.05). The metabolic activity for propranolol was examined using the hepatic microsomal fraction prepared from control and ARF rats. There was no significant difference in the kinetics of oxidative metabolism of propranolol between two groups. These results suggest that the previously reported decrease in the hepatic clearance of propranolol in ARF is due to decreased hepatic uptake of the drug from the blood into the liver cells.     

Effect of thymoquinone on hepatorenal dysfunction and alteration of CYP3A1 and spermidine/spermine N-1-acetyl-transferase gene expression induced by renal ischaemia-reperfusion in rats

Objectives Renal ischaemia–reperfusion (I/R) is a well‐characterised model of acute renal failure that causes both local and remote organ injury. The aim of this work was to investigate the effect of thymoquinone, the main constituent of the volatile oil extracted from Nigella sativa seeds, on renal and hepatic changes after renal ischaemia–reperfusion. Methods Male Sprague‐Dawley rats were divided into sham I/R vehicle‐treated groups, and I/R thymoquinone‐treated groups. Thymoquinone (10 mg/kg, p.o.) was administered for ten consecutive days to the I/R thymoquinone group before injury. I/R and I/R thymoquinone groups were subjected to 30‐min ischaemia followed by 4‐h reperfusion. Key findings I/R resulted in a significant increase in malondialdehyde (MDA) level and decreases in glutathione‐S‐transferase (GST) and superoxide dismutase (SOD) activity in liver and kidney tissues. Thymoquinone treatment caused the reversal of I/R‐induced changes in MDA as well as GST and SOD activity. Moreover, I/R caused a significant rise in creatinine and alanine aminotransferase serum levels. CYP3A1 mRNA expression was induced significantly by I/R in both liver and kidney tissues compared with sham group. Thymoquinone reduced significantly this increase. I/R caused induction of mRNA expression of spermidine/spermine N‐1‐acetyl‐transferase (SSAT), a catabolic enzyme that participates in polyamine metabolism, in liver and kidney tissues. Thymoquinone reduced SSAT mRNA expression significantly in liver and markedly in kidney. Conclusions These findings suggested that thymoquinone protected against renal I/R‐induced damage through an antioxidant mechanism as well as the decrease of CYP3A1 and SSAT gene expression.     

Differential activities of CYP1A isozymes in hepatic and intestinal microsomes of control and 3-methylcholanthrene-induced rats

Differences in expression of CYP1A isoforms (CYP1A1 and CYP1A2) in liver and small intestine of male Wistar rats and their inducibility by 3-methylcholanthrene as well as the effect of different CYP1A1/1A2 expression on caffeine metabolism were investigated. In rat liver, CYP1A2 is the predominant isoform and CYP1A1 protein expression in liver is significantly increased after treatment by 3-methylcholanthrene. In contrast, only CYP1A1 was detected in control and 3-methylcholanthrene induced small intestine microsomes. Treatment with 3-methylcholanthrene (40 mg/kg intraperitoneally daily during 1, 2, 3 or 4 days) demonstrated that liver CYP1A1 is more sensitive for the induction effects than CYP1A2 and also that significant induction of CYP1A1 in rat small intestine only occurred after 3 to 4 days pretreatment. Caffeine metabolism and inhibition studies by furafylline, CYP1A1 antiserum and ketoconazole revealed that the differences in the expression of CYP1A1 and CYP1A2 in the two tissues led to significant changes in the contribution of the various isoenzymes involved in the biotransformation of caffeine. Whereas in liver paraxanthine formation was almost exclusively catalyzed by CYP1A2, in rat proximal intestine it was formed by CYP1A1. In addition, other CYP enzymes (most probably CYP3A) play a significant role in theobromine and theophylline formation from caffeine in rat intestine. Overall, this study shows different expression and inducibility of CYP1A1/1A2 by 3-methylcholanthrene in rat liver and small intestine. Furthermore in rat intestine cytochrome P450 isozymes such as CYP1A1 and CYP3A replace CYP1A2 in the caffeine metabolism.