Phenobarbital Group Research Articles

Does phenobarbital improve the effectiveness of therapeutic hypothermia in infants with hypoxic-ischemic encephalopathy?

To determine whether phenobarbital (PB) given before therapeutic hypothermia to infants with hypoxic-ischemic encephalopathy (HIE) augments the neuroprotective efficacy of hypothermia. Records of 68 asphyxiated infants of 36 weeks' gestation, who received hypothermia for moderate or severe HIE were reviewed. Some of these infants received PB prophylactically or for clinical seizures. All surviving infants had later brain magnetic resonance imaging (MRI). The composite primary outcome of neonatal death related to HIE with worsening multiorgan dysfunction despite maximal treatment, and the presence of post-hypothermia brain MRI abnormalities consistent with hypoxic-ischemic brain injury, were compared between the infants who received PB before initiation of hypothermia (PB group, n=36) and the infants who did not receive PB before or during hypothermia (No PB group, n=32). Forward logistic regression analysis determined which of the pre-hypothermia clinical and laboratory variables predict the primary outcome. The two groups were similar for severity of asphyxia as assessed by Apgar scores, initial blood pH and base deficit, early neurologic examination, and presence of an intrapartum sentinel event. The composite primary outcome was more frequent in infants from the PB group (PB 78% versus No PB 44%, P=0.006, odds ratio 4.5, 95% confidence interval 1.6 to 12.8). Multivariate analysis identified only the PB receipt before initiation of hypothermia (P=0.002, odds ratio 9.5, 95% confidence interval 2.3 to 39.5), and placental abruption to be independently associated with a worse primary outcome. PB treatment before cooling did not improve the composite outcome of neonatal death or the presence of an abnormal post-hypothermia brain MRI, but the long-term outcomes have not yet been evaluated.

Effect of high-dose phenobarbital on oxidative stress in perinatal asphyxia: An open label randomized controlled trial

To evaluate the effect of high dose phenobarbital on lipid peroxidation and antioxidant enzymes in perinatal asphyxia. Open label, Randomized controlled trial. Neonatal intensive care unit of a tertiary care teaching hospital. 72 full term inborn neonates with severe birth asphyxia. Neonates were randomized to Study (phenobarbital) group and Control group. The infants in the study group received phenobarbital infusion (40 mg/kg) within first two hours of life while babies in the control group did not receive any phenobarbital. Rest of the management in both the groups was as per the unit protocol for the management of hypoxic ischemic encephalopathy. A cerebrospinal fluid examination was done at 12 ± 2 hours of life to determine the levels of superoxide dismutase, glutathione peroxidise and malonyldialdehyde. 60 neonates were followed up at 1 month of age when a detailed neurological examination was done. Four neonates in the study group and six neonates in the control group died during the study. Two neonates in the study group were lost to follow up. The cerebrospinal fluid lipid peroxides and antioxidant enzymes were significantly lower in the phenobarbital group as compared to the control group. The neurological outcome at one month follow up was found to be comparable between the two groups. Phenobarbital (40 mg/kg) given in the first two hours of life in term neonates with perinatal asphyxia led to a decrease in CSF levels of lipid peroxides and antioxidant enzymes at 12 ± 2 hours of life.

191 Does Phenobarbital Improve the Effectiveness of Therapeutic Hypothermia in Infants with Hypoxic-Ischemic Encephalopathy?

Objective: To determine whether Phenobarbital (PB) given before therapeutic hypothermia to infants with hypoxic-ischemic encephalopathy (HIE) augments the neuroprotective efficacy of hypothermia.Methods: Records of 68 asphyxiated infants of ≥ 36 weeks' gestation, who received hypothermia for moderate or severe HIE were reviewed. Some of these infants received PB prophylactically or for clinical seizures. All surviving infants had later brain MRI. The composite primary outcome of HIE-related neonatal death, and MRI abnormalities consistent with hypoxic-ischemic brain injury, were compared between the infants who received PB before initiation of hypothermia (PB group, n= 36) and the infants who did not receive PB before or during hypothermia (no PB group, n= 32). Logistic regression analysis determined which of the pre-hypothermia clinical and laboratory variables predict the primary outcome.Results: The two groups were similar for severity of asphyxia as assessed by Apgar scores, initial blood pH and base deficit, early neurologic examination, and presence of an intrapartum sentinel event. The composite primary outcome was more frequent in infants from the PB group (PB 78% versus No PB 44%, p=0.006, OR 4.5, 95% CI 1.6 12.8). Multivariate analysis identified only the PB receipt before initiation of hypothermia (p=0.002, OR 9.5, 95% CI 2.3 39.5), and placental abruption to be independently associated with a worse primary outcome.Conclusions: The combination of therapeutic hypothermia and PB may be associated with an increase in the composite outcome of HIE-related neonatal death and the brain MRI abnormalities, but the long term outcomes have not yet been evaluated.

CHANGING IN THYROID FUNCTION TEST IN CHILDREN UNDERWENT ANTIEPILEPTIC THERAPY

Objective To determine the changes in thyroid function tests in children who underwent antiepileptic therapy in Shahid Beheshti Hospital, Kashan, in 2008. Materials & Methods This analytical-observational study was carried out in a cohort fashion without an external control group (self controlled) on 45 children with new onset epilepsy who had not been previously treated with antiepileptic medications. Three subjects were excluded from the study because of presenting clinical symptoms of hypothyroidism. Plasma levels of TSH, T3, FT3, T4 and FT4 hormones were measured and compared at baseline and 3 and 6 months after treatment. Results The results of Mann-Whitney statistical analysis suggested that the increase in the plasma level of TSH was significant only in the Sodium Valproate group. The plasma level of T3 significantly decreased 3 and 6 months after treatment in the Phenobarbital group while the plasma level of FT3 significantly decreased only in the Sodium Valproate group. The decrease in T4 plasma level was significant in all groups (Carbamazepine group, Sodium Valproate group and Phenobarbital group) 3 and 6 months after the onset of treatment but the decreasing in FT4 plasma level was only significant in the Carbamazepine group 6 months after the commencement of treatment. Conclusion Phenobarbital had the least effect on thyroid hormones. Considering the effect of such medications on thyroid function tests, it seems necessary to check the plasma levels of hormones periodically after beginning the treatment.

Prophylactic Phenobarbital and Whole-Body Cooling for Neonatal Hypoxic-Ischemic Encephalopathy

In infants with hypoxic-ischemic encephalopathy, cooling reduces death/neurodevelopmental impairment, whereas prophylactic anticonvulsants may not. This retrospective analysis shows no reduction in neurodevelopmental impairment (23% in prophylactic phenobarbital group vs 45% in controls, P = .3) but fewer clinical seizures in cooled infants who received prophylactic phenobarbital (15% vs 82% P < .0001).

Implementation of a Symptom-Triggered Benzodiazepine Protocol for Alcohol Withdrawal in Family Medicine Inpatients

Purpose The purpose of this pilot study was to review the implementation of symptom-triggered benzodiazepine therapy and evaluate the feasibility and outcomes as compared with a previous hospital standard of fixed-dose phenobarbital protocol for alcohol withdrawal on a family medicine service. Methods This retrospective chart review of 46 patients' medical records was performed on admissions to the family medicine service occurring between February and October of 2005 compared with February and October of 2006. Included in the study were adults who were suffering from alcohol withdrawal symptoms (AWS), who admitted to heavy daily alcohol intake, who were intoxicated on admission, and who had a history of AWS and/or history of AWS-related seizures. The Clinical Institute Withdrawal Assessment for Alcohol Scale, Revised (CIWA-Ar) was used to evaluate the impact of individualized symptom-triggered therapy on outcome measurements utilizing symptom-triggered benzodiazepine therapy compared with the previous hospital standard using a fixed-dose phenobarbital protocol. Results One hundred percent of the patients in the phenobarbital group required drug compared with 38% in the benzodiazepine group ( P &lt; 0.001). Fewer patients (9.5%) in the benzodiazepine group left the hospital against medical advice (AMA), while 36% of patients in the phenobarbital group left AMA ( P = 0.045). There was no significant difference in length of stay or the number of days on the protocol. Conclusion The results of the pilot study demonstrated that symptom-triggered therapy using benzodiazepines resulted in better outcomes than fixed-dosing phenobarbital. Importantly, most patients in the benzodiazepine group required no drug administration.

Effect of memantine on plasma concentrations of carbamazepine and phenytoin in rats: A controlled experimental study

Background: Elderly patients, especially those with Alzheimer's disease, may be prescribed memantine and an antiepileptic drug concurrently. Objective: The aim of this study was to compare the interaction of memantine with phenobarbital (an enzyme inducer) and chloramphenicol (an enzyme inhibitor) on plasma concentrations of carbamazepine (CBZ), CBZ-10,11-epoxide (CBZE), and phenytoin in an experimental model. Methods: Eight groups of rats (200–230 g) were treated for 14 days each. In groups 1 and 2, phenobarbital 50 mg/kg was administered daily as an enzyme inducer 60 minutes before CBZ 50 mg/kg or phenytoin 30 mg/kg administration, respectively. In groups 3 and 4, chloramphenicol 300 mg/kg was administered daily as an enzyme inhibitor 60 minutes before CBZ or phenytoin administration, respectively. In groups 5 and 6, memantine 20 mg/kg was administered daily 60 minutes before CBZ or phenytoin, respectively. In group 7, CBZ alone was administered daily; in group 8, phenytoin alone was administered daily. Two hours after the last intragastric gavage, animals were anesthetized with ether and 2 mL of blood was drawn from the heart into a syringe containing EDTA. A validated method developed in this study was used for simultaneous determination of CBZ, CBZE, and phenytoin concentrations in rat plasma. Results: The study comprised 8 groups of 9 male adult Wistar rats each. Compared with groups 7 and 8, concurrent use of CBZ or phenytoin with phenobarbital (groups 1 and 2) was associated with significantly lower mean (SEM) plasma concentrations of CBZ (3.45 [0.16] vs 2.20 [0.21] μg/mL; P < 0.001) and phenytoin (3.68 [0.09] vs 1.63 [0.15] μg/mL; P < 0.001) and a significantly higher plasma CBZE concentration (9.85 [0.29] vs 11.18 [0.29] μg/mL; P < 0.05). Concurrent use of CBZ or phenytoin with chloramphenicol (groups 3 and 4) was associated with significantly higher plasma concentrations of CBZ (4.81 [0.17] μg/mL; P < 0.001) and phenytoin (6.24 [0.22] μg/mL; P < 0.001) and a significantly lower plasma CBZE concentration (3.88 [0.25] μg/mL; P < 0.001). Concurrent use of CBZ or phenytoin with memantine (groups 5 and 6) was not associated with a significant change in the plasma concentration of CBZ, CBZE, or phenytoin. Conclusion: Memantine was not associated with a significant change in the plasma concentration of CBZ, CBZE, or phenytoin in this experimental model.

Long‐term antiepileptic drug administration during early life inhibits hippocampal neurogenesis in the developing brain

Certain antiepileptic drugs (AEDs) that are commonly used to treat seizures in children also affect cognition, and these effects can persist into adulthood, long after drug withdrawal. Widespread enhancement of apoptosis may be one mechanism underlying these lasting cognitive changes. Whether AEDs affect other processes in brain development during early postnatal life has not, however, been systematically analyzed. Here we determined whether chronic administration of common AEDs during early life alters cell proliferation and neurogenesis in the hippocampus. Postnatal day 7 (P7) rats received phenobarbital, clonazepam, carbamazepine, valproate, topiramate, or vehicle for 28 days. Bromodeoxyuridine was administered on P34 to label dividing cells. Cell proliferation was assessed 24 hr later, and cell survival and differentiation were assessed 28 days later. Phenobarbital and clonazepam significantly inhibited cell proliferation by 63% and 59%, respectively, and doublecortin immunoreactivity (indicator of neurogenesis) in the dorsal hippocampus was also significantly decreased by 26% and 24%, respectively. Survival of new cells steadily decreased in phenobarbital and clonazepam groups over 28 days. Reduced cell proliferation and survival resulted in fewer new neurons in the dentate gyrus, as confirmed by neuronal counting on P62. There were, however, no differences in cell distribution pattern or differentiation toward neuron and glial cells when phenobarbital and clonazepam groups were compared with controls. There were no changes in rats exposed to carbamazepine, valproate, or topiramate. Thus, inhibiting cell proliferation, survival, and neurogenesis in the developing hippocampus may be another potential mechanism underlying brain impairment associated with certain AED therapies in early life.

Effects of Ethanol and Phenobarbital on Hemoglobin Adducts Formation in Rats Exposed to Benzidine and Direct Black 38

The objective of this study was to evaluate the effects of pretreatment of ethanol (EtOH) and phenobarbital (PB), which are known to affect the metabolism of xenobiotics, in the formation of hemoglobin adducts in rats administered with benzidine (BZ) and Direct Black 38 (DB38). The experimental rats were divided into BZ and DB38 groups; each group was subdivided into control, EtOH, and PB groups. Blood samples were separated into hemoglobin and plasma immediately after obtaining and basic hydrolysis was done to convert the adducts into aromatic amines. Hydrolyzed BZ, monoacetylbenzidine (MABZ), and 4-aminobiphenyl (4ABP) were separated by reversed-phase liquid chromatography without derivatization. Then, quantitative analyses were performed using a high performance liquid chromatograph equipped with an electrochemical detector. The amount of metabolites was expressed in the hemoglobin binding index (HBI). As a result, the formations of hemoglobin in BZ-, MABZ-, and 4ABP-HBI of BZ-EtOH and BZ-PB groups were increased compared with those of BZ-control group. In DB38 group, all of HBIs except for BZ-HBI were increased more than those of DB38-control group regardless of the pretreatment. These results are attributable to the fact that EtOH and PB induced N-hydroxylation is related to the formation of hemoglobin adducts. They indicate that EtOH not only increases the adduct formation by inducing N-hydroxylation but also induces N-acetylation. PB induced N-hydroxylation and increased the adduct formation in BZ group, but decreased the adduct formation in DB38 group due to decreasing azo reduction. These results suggest that the effects of EtOH or PB should be considered in biochemical monitoring of BZ and DB38 for the assessment of intermittent exposure to BZ and DB38.

COMPARISON BETWEEN DIAZEPAM AND PHENOBARBITAL IN PREVENTION OF FEBRILE SEIZURE: CLINICAL TRIAL

Abstract Objective Febrile convulsions (FC) are the most common convulsive events in childhood, occurring in 2-5% of children. About one third of these children will have a recurrence during a subsequent febrile infection. This sudden neurologic problem is extremely frightening and emotionally traumatic for parents so some physicians try to prevent recurrence of FC by prescribing different drugs. Materials and Methods This is a randomized clinical trial in 85 healthy children, aged 6 months to 5 years, who were not treated before. These children received randomly either oral diazepam (0.33 mg/kg/TDS for two days during febrile illness) or continuous oral Phenobarbital (3-5mg/kg /24 h). Results Ultimately 64 patients completed the study and were followed up for an average of 13 months (12-18 months). The rate of recurrence of febrile seizure was 18.2% in diazepam group and 32.3% in Phenobarbital group; the difference is not statistically significant (p=0.16). Conclusion There was no significant difference between intermittent oral diazepam and continuous oral Phenobarbital for FC prevention.

Global liver proteomics of rats exposed for 5 days to phenobarbital identifies changes associated with cancer and with CYP metabolism.

A global proteomics approach was applied to model the hepatic response elicited by the toxicologically well-characterized xenobiotic phenobarbital (PB), a prototypical inducer of hepatic xenobiotic metabolizing enzymes and a well-known nongenotoxic liver carcinogen in rats. Differential detergent fractionation two-dimensional liquid chromatography electrospray ionization tandem mass spectrometry and systems biology modeling were used to identify alterations in toxicologically relevant hepatic molecular functions and biological processes in the livers of rats following a 5-day exposure to PB at 80 mg/kg/day or a vehicle control. Of the 3342 proteins identified, expression of 121 (3.6% of the total proteins) was significantly increased and 127 (3.8%) significantly decreased in the PB group compared to controls. The greatest increase was seen for cytochrome P450 (CYP) 2B2 (167-fold). All proteins with statistically significant differences from control were then analyzed using both Gene Ontology (GO) and Ingenuity Pathways Analysis (IPA, 5.0 IPA-Tox) for cellular location, function, network connectivity, and possible disease processes, especially as they relate to CYP-mediated metabolism and nongenotoxic carcinogenesis mechanisms. The GO results suggested that PB's mechanism of nongenotoxic carcinogenesis involves both increased xenobiotic metabolism, especially induction of the 2B subfamily of CYP enzymes, and increased cell cycle activity. Apoptosis, however, also increased, perhaps, as an attempt to counter the rising cancer threat. Of the IPA-mapped proteins, 41 have functions which are procarcinogenic and 14 anticarcinogenic according to the hypothesized nongenotoxic mechanism of imbalance between apoptosis and cellular proliferation. Twenty-two additional IPA nodes can be classified as procarcinogenic by the competing theory of increased metabolism resulting in the formation of reactive oxygen species. Since the systems biology modeling corresponded well to PB effects previously elucidated via more traditional methods, the global proteomic approach is proposed as a new screening methodology that can be incorporated into future toxicological studies.

Resistance to Phenobarbital Extends to Phenytoin in a Rat Model of Temporal Lobe Epilepsy

Most patients who are resistant to the first antiepileptic drug (AED) treatment are also resistant to a treatment with a second or third AED, indicating that patients who have an inadequate response to initial treatment with AEDs are likely to have refractory epilepsy. Animal models of refractory epilepsy are important tools to study mechanisms of AED resistance and develop new treatment strategies for counteracting resistance. We have recently described a rat model of temporal lobe epilepsy (TLE), in which spontaneous recurrent seizures (SRS) develop after a status epilepticus induced by sustained electrical stimulation of the basolateral amygdala. Prolonged treatment of epileptic rats with phenobarbital (PB) resulted in two subgroups, PB responders and PB nonresponders. In the present study we examined if rats with PB-resistant seizures are also resistant to phenytoin (PHT), using continuous EEG/video recording of spontaneous seizures. First, a new group of 15 epileptic rats was produced and selected by treatment with PB into responders (8 rats) and nonresponders (6 rats), respectively. During subsequent treatment with PHT, the doses of PHT had to be individually adjusted for each rat to avoid toxicity. Treatment with PHT led to complete seizure control in two animals and a >50% reduction of seizure frequency in three other rats, which were considered PHT responders. In nine of the remaining rats, PHT did not exert any clear anticonvulsant effect, so that these rats were considered nonresponders. Plasma levels of PHT did not differ significantly between responders and nonresponders. When comparing the PB and PHT nonresponder groups, five of the six PB-resistant rats (83%) were also resistant to PHT, demonstrating that rats that have an inadequate response to initial treatment with PB are likely to be also resistant to treatment with a second AED. The AED-resistant rats of our model meet the definition of pharmacoresistance in animal models, that is, persistent seizure activity not responding to at least two AEDs at maximum tolerated doses. This new model of pharmacoresistant TLE may be useful in the targeted development of new therapies for refractory epilepsy.

Side effects of phenobarbital and carbamazepine in childhood epilepsy: randomised controlled trial

Objective To compare the behavioural side effects associated with two commonly used antiepilepsy drugs—phenobarbital and carbamazepine—in children in Bangladesh.Design Prospective randomised controlled single centre trial. Setting Specialist children's hospital in...

A randomized controlled trial of phenobarbital in neonates with hypoxic ischemic encephalopathy

Background. Phenobarbital is one of the oldest, cheapest and most easily available cerebro-protective drugs for the hypoxic brain. It has multiple actions that could be of benefit to the asphyxiated brain. However, its potential has not been fully explored.Objective. To study the effect of phenobarbital given within six hours of life to term and near-term asphyxiated neonates, on mortality, neurological abnormality at discharge and seizures.Methods. This was a randomized controlled trial set in a tertiary care referral perinatal centre. Asphyxiated neonates (gestational age ⩾34 weeks) manifesting with hypoxic ischemic encephalopathy (HIE) in the first six hours of life were randomized to receive either injection of phenobarbital 20 mg/kg IV or to the control group. The primary outcome was death or abnormal neurological examination at discharge while seizures, need for ventilation and multi-organ dysfunction were secondary outcomes.Results. Twenty-five babies received phenobarbital and 20 were in the control group. The mortality (20% vs. 15%) and abnormal neurological outcome at discharge (30% vs. 53%, p = 0.15) were statistically not different between the two groups. In the phenobarbital group, 8% of neonates developed seizures while 40% of babies in the control group developed seizures (p = 0.01, relative risk (RR) = 0.20 (0.05–0.84)). Phenobarbital was well tolerated and did not increase the need for respiratory support.Conclusions. Phenobarbital in the dose of 20 mg/kg IV given within six hours of life to term and near-term neonates with HIE, significantly decreased the incidence of neonatal seizures and was well tolerated. However, it did not alter the mortality and neurologic outcome at discharge.

A Randomized, Triple-Blind, Placebo-Controlled Trial of Prophylactic Oral Phenobarbital to Reduce the Need for Phototherapy in G6PD-Deficient Neonates

Decreased conjugation is probably more important than hemolysis for causing jaundice in G6PD-deficient neonates. The role of enzyme inducers, like phenobarbital, in G6PD deficiency is unclear. This randomized controlled trial was performed to evaluate Phenobarbital's role in reducing the need for phototherapy among G6PD-deficient neonates. This stratified, randomized, triple-blinded, placebo-controlled trial was conducted in a level III NICU. Consecutive babies with gestation >/=34 weeks and birth weight >/=1800 g were screened from cord blood. G6PD-deficient neonates, who were otherwise healthy, were enrolled. Rh isoimmunization, maternal Phenobarbital use and lack of parental consent were exclusion criteria. Subjects were randomly allocated to receive 5 mg/kg day of oral phenobarbital/ placebo for first 3 days. They were monitored daily for total serum bilirubin (TSB) until declining TSB was documented twice. The primary outcome was requirement for phototherapy and secondary outcomes were duration of phototherapy, need for exchange transfusion, peak TSB and adverse effects. Sample size of 56 could detect a decline in phototherapy requirement from 40 to 5% with 80% power and 5% error. Of 2370 babies screened, 63 were G6PD-deficient. Of them, 56 eligible babies were allocated to phenobarbital (n=27) or placebo (n=29). The mean age of administration of the first dose was 18.55+/-7.3 h. In total, 44% in phenobarbital group and 41% in placebo group required phototherapy (p=1.0). There was no significant difference in exchange transfusion rates (18.5 vs 10%, p=0.46). No baby had adverse reactions. Prophylactic oral phenobarbital does not decrease the need for phototherapy or exchange transfusions in G6PD-deficient neonates.

Evaluation of mutant frequencies of chemically induced tumors and normal tissues in ?/cII transgenic mice

Genomic instability has been implicated as an important component in tumor progression. Evaluation of mutant frequencies (MFs) in tumors of transgenic mice containing nontranscribed marker genes should be useful for quantitating mutation rates in tumors as the physiologically inactive transgene provides neither a positive nor a negative selective pressure on the tumor. We have conducted long-term carcinogenicity studies in lambda/cII transgenic B6C3F1 mice using a variety of genotoxic and nongenotoxic test agents and have evaluated the mutant frequencies in both tumors and normal tissues from these animals. Mice were administered diethylnitrosamine (DEN) as three intraperitoneal injections of 15 mg/kg; phenobarbital (PB) or oxazepam (OXP) provided ad libitum at 0.1% or 0.25% in the diet, respectively; DEN initiation plus PB in the diet; or urethane (UTH) provided ad libitum at 0.2% in the drinking water. Normal tissues and tumors were isolated at various times over a 2-year period and half of each tissue/tumor was evaluated histopathologically and the other half was evaluated for MF in the cII transgene. Approximately 20 mutants from each of 166 individual tissues (tumor and nontumor) were sequenced to determine whether increases in MF represented unique mutations or were due to clonal expansion. UTH produced significant increases in MF in normal liver and lung. DEN either with or without PB promotion produced significant increases in MF in liver and correction of MF for clonality produced little change in the overall MF in these groups. PB produced a twofold increase in liver MF over controls after 27 weeks of treatment, but a similar increase was not observed with longer dosing times; at later time points, the MF in the PB groups was lower than that of the control group, suggesting that PB is not producing direct DNA damage in the liver. OXP failed to produce an increase in MF over controls, even after 78 weeks of treatment. Selected cases of genomic instability were observed in tumors from all treatments except OXP, with individual liver tumors showing very high MF values even after clonal correction. One rare and interesting finding was noted in a single mouse treated with UTH, where a mammary metastasis had an MF approximately 10-fold greater than the parent tumor, with 75% of the mutations independent, providing strong evidence of genomic instability. There was no clear correlation between tumor phenotype and MF except that pulmonary adenomas generally had higher MFs than normal lung in both genotoxic and nongenotoxic treatment groups. Likewise, there was no correlation between tumor size and MF after correction for clonality. The results presented here demonstrate that individual tumors can show significant genomic instability, with very significant increases in MF that are not attributed to clonal expansion of a single mutant cell.

Microarray analysis on CYPs expression in pregnant rats after treatment with pregnenolone-16α-carbonitrile and phenobarbital

We previously reported the protein expression profiles of nine cytochrome P450 isozymes (CYPs) in pregnant rat's liver, fetal liver, and placenta after treatment with pregnenolone-16α-carbonitrile (PCN), dexamethasone (DEX), or phenobarbital (PB). In this study, the gene expression of 40 CYPs and 2 orphan nuclear receptors for CYP inducers, that is, Nr1i2 (CYP3A subfamily inducible by PCN) and Nr1i3 (CYP2B subfamily inducible by PB), in pregnant rat's liver, fetal liver, and placenta was investigated at one time. Fischer 344 (F344) pregnant rats were daily treated intraperitoneally with 50 mg/kg of PCN or 80 mg/kg of PB from 13 to 16 days of gestation (DG). They were sacrificed on 17 DG, and microarray analysis using Affymetrix Rat Expression Array 230A was performed. Ten genes expression significantly increased in dam's liver in PCN group, and seven genes expression in PB group. On the other hand, four genes expression increased in fetal liver in PCN group, and three genes expression increased in PB group. Being common to dam's and fetal livers, the gene expression of Cyp3A1 (CYP3A subfamily) and cytochrome P-450e (CYP2B subfamily) increased in both PCN and PB groups. In placenta, the expression of Cyp3A1 gene was significantly induced in PB group, and it also showed a tendency to increase in PCN group. The expression of Nr1i2 gene was significantly elevated only in dam's liver of PCN group, while the expression of Nr1i3 gene showed no changes in all groups. The results of the present study of 40 CYPs gene expression mostly corresponded to our previous reports on 9 CYPs protein expression.

Effects of microsome enzyme induced by phenobarbarbital on the stereoselectivity of recemic propranolol glucuronidation metabolism

To study the stereoselectivity of R-(+) and S-(-)-propranolol glucuronidation and metabolic interaction between R(+)- and S-(-)-propranolol. A RP-HPLC analytical method was developed for determination of R-(+)-and S-(-)-propranolol glucuronide (PG) incubated with rat hepatic microsome induced with phenobarbital (PB). The method was applied to investigate the stereoselectivity metabolism of racemic propranolol glucuronidation in vitro. In control and PB group, the concentration of R-(+)-PG produced at different substrates was higher than that of S-(-)-PG. Compared with the control, the V(max) and Cl(int) for R(+)-and S-(-)-propranolol increased significantly the K(m) for R(+)-propranolol was elevated, while that for S-(-) propranolol was decreased. There is a stereoselectivity in glucuronidation of propranolol in rat hepatic microsome induced with PB and R-(+)-propranolol is preferred. Metabolic interaction between R-(+)-and S-(-)-propranolol exists with a concentration-dependent mode.

586 Induction of cytochrome P450 mRNA by typical inducers in rat hepatoma cell line

We previously reported the protein expression profiles of nine cytochrome P450 isozymes (CYPs) in pregnant rat's liver, fetal liver, and placenta after treatment with pregnenolone-16α-carbonitrile (PCN), dexamethasone (DEX), or phenobarbital (PB). In this study, the gene expression of 40 CYPs and 2 orphan nuclear receptors for CYP inducers, that is, Nr1i2 (CYP3A subfamily inducible by PCN) and Nr1i3 (CYP2B subfamily inducible by PB), in pregnant rat's liver, fetal liver, and placenta was investigated at one time. Fischer 344 (F344) pregnant rats were daily treated intraperitoneally with 50 mg/kg of PCN or 80 mg/kg of PB from 13 to 16 days of gestation (DG). They were sacrificed on 17 DG, and microarray analysis using Affymetrix Rat Expression Array 230A was performed. Ten genes expression significantly increased in dam's liver in PCN group, and seven genes expression in PB group. On the other hand, four genes expression increased in fetal liver in PCN group, and three genes expression increased in PB group. Being common to dam's and fetal livers, the gene expression of Cyp3A1 (CYP3A subfamily) and cytochrome P-450e (CYP2B subfamily) increased in both PCN and PB groups. In placenta, the expression of Cyp3A1 gene was significantly induced in PB group, and it also showed a tendency to increase in PCN group. The expression of Nr1i2 gene was significantly elevated only in dam's liver of PCN group, while the expression of Nr1i3 gene showed no changes in all groups. The results of the present study of 40 CYPs gene expression mostly corresponded to our previous reports on 9 CYPs protein expression.

Effect of oral administration of low doses of pentobarbital on the induction of cytochrome P450 isoforms and cytochrome P450-mediated reactions in immature Beagles.

To determine the effect of oral administration of low doses of pentobarbital on cytochrome P450 (CYP) isoforms and CYP-mediated reactions in immature Beagles. 42 immature (12-week-old) Beagles. Dogs were grouped and treated orally as follows for 8 weeks: low-dose pentobarbital (50 microg/d; 4 males, 4 females), mid-dose pentobarbital (150 microg/d; 4 males, 4 females), high-dose pentobarbital (500 microg/d; 4 males, 4 females), positive-pentobarbital control (10 mg/kg/d; 2 males, 2 females), positive-phenobarbital control (10 mg/kg/d; 2 males, 2 females), and negative control (saline 10.9% NaCl] solution; 5 males, 5 females). Serum biochemical and hematologic values were monitored. On necropsy examination, organ weights were determined, and histologic evaluation of tissue sections of liver, kidney, small intestine, testes, epididymis, and ovaries was performed. Hepatic and intestinal drug-metabolizing enzyme activities were measured, and relative amounts of CYP isoforms were determined by western blot analysis. The amount of a hepatic CYP2A-related isoform in dogs from the high-dose pentobarbital treatment group was twice that of dogs from the negative control group. CYP2C was not detectable in small intestinal mucosa of dogs from the negative control group; measurable amounts of CYP2C were found in dogs from the various (low-, mid-, and high-dose) pentobarbital treatment groups and from positive-pentobarbital and positive phenobarbital control groups. Several CYP-mediated reactions increased in a dose-dependent manner. The lowest calculated effective dose of pentobarbital ranged from 200 to 450 microg/d. Several CYP isoforms and their associated reactions were induced in dogs by oral administration of low amounts of pentobarbital.