Proteomic and Bioinformatics Analysis of Membrane Lipid Domains after Brij 98 Solubilization of Uninduced and Phenobarbital-Induced Rat Liver Microsomes: Defining the Membrane Localization of the P450 Enzyme System.

The proteomes of ordered and disordered lipid microdomains in rat liver microsomes from control and phenobarbital (PB)-treated rats were determined after solubilization with Brij 98 and analyzed by tandem mass tag (TMT)-liquid chromatography-mass spectrometry (LC-MS). This allowed characterization of the liver microsomal proteome and the effects of phenobarbital-mediated induction, focusing on quantification of the relative levels of the drug-metabolizing enzymes._The microsomal proteome from control rats was represented by 333 (23%) proteins from ordered lipid microdomains, 517 (36%) proteins from disordered lipid domains, and 587 (41%) proteins that uniformly distributed between lipid microdomains. Most enzymes related to drug metabolism were mainly localized in disordered lipid microdomains. However, cytochrome P450 (CYP) 1A2, multiple forms of CYP2D, and several forms of UDP glucuronosyltransferases (UGT) 1A1 and 1A6) localized to ordered lipid microdomains. Other drug-metabolizing enzymes, including several forms of cytochromes P450, were uniformly distributed between the ordered and disordered regions. The redox partners, NADPH-cytochrome P450 reductase and cytochrome b5, localized to disordered microdomains. PB induction resulted in only modest changes in protein localization. Less than five proteins were variably associated with the ordered and disordered membrane microdomains in PB and control microsomes. PB induction was associated with fewer proteins localizing in the disordered membranes and more being uniformly distributed or localized to ordered domains. Ingenuity Pathway Analysis (IPA) was used to ascertain the effect of PB on cellular pathways, resulting in attenuation of pathways related to energy storage/utilization and overall cellular signaling and an increase in those related to degradative pathways. SIGNIFICANCE STATEMENT: This work identifies the lipid microdomain localization of the proteome from control and phenobarbital-induced rat liver microsomes. Thus, it provides an initial framework to understand how lipid/protein segregation influences protein-protein interactions in a tissue extract commonly used for studies in drug metabolism and uses bioinformatics to elucidate the effects of phenobarbital induction on cellular pathways.

A 28-day whole-body inhalation study to evaluate octamethylcyclotetrasiloxane (D4) absorption/distribution in two rat strains.

To investigate the potential toxicity of Octamethylcyclotetrasiloxane (D4), studies in laboratory rats have used primarily one of two strains, Sprague-Dawley (SD) and Fischer-344 (F-344). Reproductive studies used SD rats whereas F-344 rats were used in D4 pharmacokinetics, metabolism, acute/subacute/chronic toxicity and oncogenicity studies. Here, we assessed specific endpoints related to D4 pharmacokinetics and biochemistry in SD and F-344 rats within a single study, which allows for direct comparisons between strain and sex. This assessment included determination of microsomal total P450, NADPH-cytochrome c reductase, epoxide hydrolase, CYP2B1/2, CYP1A1/2, CYP3A1/2, CYP2C11, and CYP2A1. Aside from slight brown pigment in the liver, the treated animals experienced no toxicologically significant weight loss, decrease in food consumption, or clinical signs. Concentrations of D4 in plasma and fat were generally greater in females relative to males in both strains. SD females appeared to have statistically significantly greater plasma and fat concentrations following 28 days of repeated exposure to D4 relative to F-344 rats, suggesting the existence of potential sex and strain differences in D4 pharmacokinetics. The effect of D4 exposure on liver enzyme expression was similar among and between sexes and strain and was consistent with that for phenobarbital-like inducers. Notable differences included a finding of elevated CYP2B1/2 protein levels without a similar magnitude of increase in CYP2B/1 activity and a greater degree of CYP3A1/2 induction (protein and activity) for female SD rats. The importance of these findings is unclear, however reduced CYP2B1/2 activity may give rise to lower rates of D4 metabolism and clearance, consistent with the higher tissue levels of D4 in SD relative to F-344 female rats.

Reversal of ethinyl estradiol-induced bile secretory failure with Triton WR-1339.

The effects of Triton WR-1339 and phenobarbital on ethinyl estradiol bile secretory failure were examined to determine the mechanism responsible for decreased bile salt excretion. When administered to ethinyl estradiol-treated rats, Triton WR-1339 restored bile salt independent bile flow and maximum taurocholate transport, whereas phenobarbital corrected bile flow only. Ethinyl estradiol decreased the activities of Na(+)-K(+)-ATPase, 5'-nucleotidase, while increasing the activities of Mg(++)-ATPase and alkaline phosphatase. In contrast to these heterogeneous changes in surface membrane enzyme activities, the number and affinity of [(14)C]cholic acid carriers were not altered. When administered in vivo or added directly to surface membrane fractions Triton WR-1339 restored the activities of Na(+)-K(+)-ATPase and Mg(++)-ATPase of rats treated with ethinyl estradiol through a process that did not require protein synthesis (unaffected by cycloheximide). Phenobarbital also restored the activity of Na(+)-K(+)-ATPase to control levels, but, unlike Triton WR-1339 it did not correct the defect responsible for reduced bile salt secretion. Ethinyl estradiol increased the concentration of cholesterol esters in surface membrane fractions. When administered to ethinyl estradiol-treated rats, Triton WR-1339 restored cholesterol ester concentrations to normal, whereas phenobarbital did not. These combined data suggest that decreased or altered bile salt carriers or reduced sodium driving forces resulting from impaired activity of Na(+)-K(+)-ATPase are not responsible for decreased bile salt excretion in ethinyl estradiol-treated rats. It is proposed that the diverse changes in surface membrane function, which are associated with ethinyl estradiol bile secretory failure, may be the result of a generalized alteration in membrane lipid structure.

Enhancement of hepatocarcinogenesis by sorbitan fatty acid ester, a liver pyruvate kinase activity-reducing substance.

Effect on hepatocarcinogenesis of dietary sorbitan fatty acid ester (SorFAE), which had been known to cause decrease in pyruvate kinase (PK) activity, was studied in rats fed a diet containing 0.06% 3'-methyl-4-dimethylaminoazobenzene (3'-Me-DAB) for 6 weeks. The incidence of hyperplastic nodules and/or hepatocellular carcinomas in the rats fed the 3'-Me-DAB diet alone was 45.0% at the end of 51 weeks, whereas the incidence in the rats fed 3'-Me-DAB diet followed by 5 or 10% SorFAE or 0.1% phenobarbital (PB) diet were 76.2, 90.5, and 95.0%, respectively. These incidences were significantly higher compared with the group fed 3'-Me-DAB diet alone (P less than .05). No tumors were observed in rats fed 10% SorFAE diet alone. The results show that SorFAE has an enhancing effect on hepatocarcinogenesis, although the effect was weak compared to that of the effective PB dose. The results seem to confirm our assumption that a chemical that causes decrease in PK activity in rat liver might promote hepatocarcinogenesis.

In vitro metabolic conversion of aflatoxins and benzo(alpha)pyrene to nucleic acid-binding metabolites.

An aflatoxin B1 metabolite was found to become covalently bound to rat liver RNA and calf thymus DNA in vitro, and it formed complexes with increased spectral absorbance in the 360 nm region. The formation of such complexes was reduced nicotinamide adenine dinucleotide phosphate and microsome dependent, was inhibited by theta-diethylaminoethyl diphenylpropylacetate-HC1, and by CO and N2, when the latter were used to replace the gas phase of the incubations. The formation of the complexes was enhanced about 2-fold with cicrosomes from phenobarbital-treated rats but not from 3-methylcholanthrene-treated rats. More binding was observed with DNA than RNA. Dentured DNA was about 70% as effective as native DNA. Nucleic acids from various sources showed the following order of binding potency: DNA from Micrococcus luteus greater than DNA from calf thymus equal to DNA from rat liver greater than RNA from rat liver greater than transfer RNA from rat liver. In the presence of reduced nicotinamide adenine dinucleotide phosphate and microsomes from phenobarbital-treated rats, aflatoxin G1 was also converted into metabolite(s) that became covalently bound to nucleic acids and formed complexes with increased spectral absorbances in the 360 nm region: this reaction was also inhibited by theta-diethylaminoethyl diphenylpropylacetate-HC1. Under the same conditions, aflatoxin B2, aflatoxin G2, aflatoxin B2a, and "Compound 11," which lack a C2-C3 double bond, did not show any noticeable binding to either DNA or RNA. These data strongly support the concept that the microsomal mixed-funciton oxygenase-catalyzed oxidation of the C2-C3 double bond of aflatoxins is a prerequisite for the formation of nucleic acid-binding metabolites. Microsomes from untreated, phenobarbital-treated, and 3-methylcholanthrene-treated rats were compared in vitro for their ability to catalyze the formation of DNA-binding metabolites from aflatozin B1 and benzo(a)pyrene. In assays involving benzo(a)pyrene, microsomes from 3-methylcholanthrene-treated rats were 12- and 5-fold more active than microsomes from untreated and phenobar-bital-treated rats, respectively. This is in contrast to the results obtained with aflatoxin B1 and suggests that different enzymes in the hepatic microsomal mixed-function oxygenase complex are involved in the generation of reactive metabolites from various polycyclic hydrocarbons.

Characterization of microsomal methyl sterol demethylase in two Morris hepatomas.

Previously, we reported that the rate of metabolism of methyl sterol intermediates of cholesterol biosynthesis by broken-cell preparations of Morriss hepatoma 7777 is very slow, whereas the intact tumors are known to synthesize cholesterol quite efficiently. Active preparations have now been obtained by substitution of pyrophosphate for phosphate buffer. Although substitution of pyrophosphate buffer markedly enhances microsomal methyl sterol demethylation rates 3- to 4-fold in hepatoma 7777, other microsomal enzymes and electron carriers in either liver or a more slowly growing hepatoma appear to be unaffected by pyrophosphate. Several properties of the active microsomal methyl sterol demethylase have now been compared for control rat liver, host liver, tumor 7777, and tumor 5123C. Conditions necessary for the assay of initial velocities of enzymic reactions in the tumor microsomes have been established with respect to the amount of protein, time-course, concentrations of cofactors and substrate, pH, and other variables. The K'm and the responses to the variables studied above are very similar for methyl sterol demethylase of microsomes isolated from control liver, host liver, tumor 5123C, and tumor 7777. The multienzymic demethylase in the various preparations has been found to be inhibited similarly by in vitro additions of cyanide, cytochrome c, and bile salts. Thus, the enzymes of the microsomal-bound 4-methyl sterol demethylase of cholesterol biosynthesis appear to be very similar in liver and these 2 Morris hepatomas. When xenobiotic inducers of microsomal oxidases, such as phenobarbital and methylcholanthrene, are administered to normal and tumor-bearing rats, elevated rates of methyl sterol demethylation are observed with isolated liver microsomes obtained from both normal and tumor-bearing rats. Similar increases are not observed in the tumors. Furthermore, daily administration of an intestinal bile acid sequestrant elevates hepatic methyl sterol demethylase, but statistically significant changes were not observed in tumors 7777 and 5123C. Since the enzymes of methyl sterol demethylase appear to be grossly similar in liver and these hepatomas, regulation of the activity of the multienzymic system contained in the tumors may be altered. On the other hand, these agents in vivo simply may not affect liver and the hepatomas similarly, due to a lack of uptake of the foreign substances by the tumor that has been transplanted to the thighs.

Clinical Pharmacology of Phenobarbital in Neonates: Effects, Metabolism and Pharmacokinetics.

Phenobarbital is an effective and safe anticonvulsant drug introduced in clinical use in 1904. Its mechanism of action is the synaptic inhibition through an action on GABAA. The loading dose of phenobarbital is 20 mg/kg intravenously and the maintenance dose is 3 to 4 mg/kg by mouth. The serum concentration of phenobarbital is up to 40 µg/ml. Nonresponders should receive additional doses of 5 to 10 mg/kg until seizures stop. Infants with refractory seizures may have a serum concentration of phenobarbital of 100 µg/ml. Phenobarbital is metabolized in the liver by CYP2C9 with minor metabolism by CYP2C19 and CYP2E1. A quarter of the dose of phenobarbital is excreted unchanged in the urine. In adults, the half-life of phenobarbital is 100 hours and in term and preterm infants is 103 and 141 hours, respectively. The half-life of phenobarbital decreases 4.6 hours per day and it is 67 hours in infants 4 week old.

Induction and activation of rat liver microsomal bile salt glucuronyltransferase.

In vivo induction and in vitro activation of the recently described bile salt glucuronyltransferase were investigated in rat. A radioactive assay for the determination of glucuronyltransferase activity was used. 14C-Labeled bile salts served as substrates, and the glucuronides were separated by thin layer chromatography. Lithocholate glucuronyltransferase activity was determined in liver microsomes of phenobarbital- and 3-methylcholanthrene-treated rats and of untreated controls. Pretreatment with phenobarbital induced lithocholate glucuronyltransferase activity to 150.5% of controls. In contrast, 3-methylcholanthrene treatment decreased activity to 29.6% of controls. In vivo activation of lithocholate glucuronyltransferase by Triton X-100 was observed in controls and in the 3-methylcholanthrene group, but not in the phenobarbital group. Substrate activation of the enzyme by lithocholate was demonstrated in microsomes of untreated controls. Pretreatment with 3-methylcholanthrene, but not phenobarbital, increased the latency of lithocholate glucuronyltransferase. The results indicate that rat liver microsomal bile salt glucuronyltransferase activity is increased by in vivo induction with phenobarbital and by in vitro activation with detergents like Triton X-100. The induction of bile salt glucuronide formation by phenobarbital is most likely one of the factors contributing to the increased biliary and fecal excretion of bile salts in patients with cholestasis following phenobarbital therapy.

Studies on the cytochrome P-450 product complexes formed during the metabolism of N,N-dimethylaniline.

The oxidative metabolism of N,N-dimethylaniline by partially solubilized cytochrome P-450 from rabbit liver was found to be associated with the formation of a 424- and 448-nm product adduct of the hemoprotein. From the effects of temperature, hydrogen ion concentration, n-octylamine, extraction of the enzyme preparations with organic solvents and pretreatment of the animals with inducers of drug metabolism on both the formation of the spectral species and the enzymic C- and N-oxidation of N,N-dimethylaniline it is concluded that the 424-nm spectral change is generated from an intermediate in the C-oxidation reaction, whereas formation of the 448-nm spectral perturbation is the result of binding to cytochrome P-450 of a metabolite arising from N-oxidation of the arylamine; N-dealkylation of the parent amine is not a obligatory intermediary step in 448-nm complex formation. The 448-nm ferrohemochrome is supposed to be formed through coordination of the N-oxidized intermediate via the oxygen atom. This type of interaction appears to require considerably stronger thermal activation as compared with the 424-nm complex. The 448-nm product adduct of cytochrome P-450 is unstable in the ferric state or in the presence of sodium dithionite.

Modulations in hepatic branch-point enzymes involved in isoprenoid biosynthesis upon dietary and drug treatments of rats.

Three branch-point enzymes of the mevalonate pathway, farnesyl pyrophosphate synthase, cis-prenyltransferase and squalene synthase were characterized in rat hepatic cytosol, microsomes and peroxisomes isolated from rats after treatment with peroxisome proliferators, inducers of the endoplasmic reticulum or modulators of lipid metabolism. Cholestyramine and phenobarbital induced primarily the cytosolic farnesyl pyrophosphate synthase, whereas clofibrate and phthalates elevated the corresponding peroxisomal activity. cis-Prenyltransferase activities in microsomes were induced 4-5-fold after clofibrate, phthalate and phenobarbital administration, but these same treatments affected the peroxisomal activity to only a limited extent. Squalene synthase activity in microsomes was completely abolished, but the peroxisomal activity was unaffected after administration of cholesterol. On the other hand, clofibrate and phthalate induced only the microsomal activities. Mevinolin treatment greatly increased peroxisomal and cytosolic farnesyl pyrophosphate synthase activities, but not the mitochondrial activity, and the cis-prenyltransferase activities were elevated in peroxisomes, but not in microsomes. These results demonstrate that the branch-point enzymes in cholesterol and dolichol biosynthesis at various cellular locations are regulated differentially and that the capacities of peroxisomes and the endoplasmic reticulum to participate in the synthesis of polyisoprenoid lipids is affected profoundly by treatment with different xenobiotics.

Effects of phenobarbital on leukocyte activation: membrane potential, actin polymerization, chemotaxis, respiratory burst, cytokine production, and lymphocyte proliferation.

Leukocyte activation is known to involve cell membrane potential changes. Phenobarbital, an anesthetic and anticonvulsant that can inhibit neuronal membrane depolarization, may also affect leukocyte activation. Measuring membrane potential, actin polymerization, chemotaxis, superoxide production, lymphocyte proliferation, intracellular calcium concentration, and cytokine production, we found that phenobarbital at a concentration of 15-30 micrograms/ml, which is considered a therapeutic serum level for controlling seizures, did not affect polymorphonuclear neutrophil (PMN) activation. At levels higher than 100 micrograms/ml, phenobarbital significantly suppressed formylmethionyl-leucyl-phenylalanine (fMLP)-induced chemotaxis. Concentrations greater than 300 micrograms/ml also inhibited phorbol myristate acetate-stimulated membrane potential change. In contrast, 30 micrograms/ml phenobarbital significantly inhibited lymphocyte proliferation stimulated by phytohemagglutinin (PHA) and pokeweed mitogen. This concentration of phenobarbital also suppressed the increase of intracellular free calcium induced by PHA. However, only a higher concentration of phenobarbital (300 micrograms/ml) was able to inhibit PHA-induced interleukin-2 (IL-2) production and suppress the proliferation of PHA-induced IL-2 receptor-bearing lymphocytes. These results suggest that concentrations of phenobarbital associated with anticonvulsive levels do not affect PMN activation but suppress lymphocyte activation, possibly by affecting intracellular signal transduction.

Tocainide kinetics and metabolism: effects of phenobarbital and substrates of glucuronyl transferase.

Tocainide, a lidocaine congener with low hepatic clearance, is eliminated predominantly by formation of a novel glucuronide conjugate. This suggested the possibility of metabolic interactions with enzyme inducers or competitive substrates for glucuronyl transferase. The time course of tocainide blood concentration as well as the urinary excretion-time profiles of drug and principal metabolite (a glucuronide of tocainide carbaminic acid, TOCG) were examined in six subjects before and after 15 days on phenobarbital (100 mg/day). In another study, the effect of salicylamide and clofibrate on the time courses of tocainide and TOCG urinary excretion were examined in four of the same six subjects. After 600 mg tocainide HCl by mouth, the area under the tocainide blood concentration-time curve was 48.2 +/- 11.9 hr micrograms/ml for the control dose and 49.6 +/- 4.2 hr micrograms/ml (mean = SD) after phenobarbital. Percent of dose excreted unchanged in urine (46.0 +/- 4.9 and 43.4 +/- 5.6) and percent of dose excreted as TOCG (30.6 +/0 3.3 and 27.7 +/- 7.2) were not affected by phenobarbital (data presented as control and after phenobarbital). Because salicylamide has been reported to be a potent inhibitor of the glucuronidation of some drugs and because clofibrate yields metabolites that may be competitive inhibitors of tocainide conjugation, the two were given together with tocainide. Average percent of dose recovered in urine as unchanged tocainide in 24 hr was 26.8%, 28.3%, and 29.7% in the control, salicylamide, and clofibrate studies. The urinary excretion of TOCG was also not affected. It is concluded that under the conditions of our investigation, the principal urinary metabolite of tocainide, a glucuronide of tocainide carbaminic acid, is formed by a mechanism not subject to induction by phenobarbital or competitive inhibition by salicylamide or clofibrate.

Kinetics of carbamazepine and carbamazepine-epoxide, determined by use of plasma and saliva.

The concentration-time curves of carbamazepine (CBZ) and its metabolite (carbamazepine-10,11-epoxide; CBZ-epoxide) were determined in patients undergoing long-term antiepileptic drug treatment with the use of plasma and saliva data. Plasma and saliva samples were assayed concurrently for each patient by liquid chromatography. There was excellent linear correlation between CBZ levels in saliva and plasma (r = 0.991, p less than 0.001) over a large concentration range. The saliva/plasma ratio for CBZ concentration was 0.26 +/- 0.01 (SD). Since CBZ binding to plasma proteins is in the order of 76%, saliva CBZ concentration seems to reflect the unbound fraction of the drug in plasma. CBZ-epoxide has not been detected in saliva. The pharmacokinetic parameters of CBZ-epoxide were determined in 6 patients. The pharmacokinetic parameters of CBZ obtained from saliva concentrations were in excellent agreement with those obtained from plasma concentrations. Thus, CBZ determination in saliva is convenient for controlling blood levels in patients as well as for studying pharmacokinetics. The half-life, the relative body clearance of CBZ, and the metabolite concentration during steady-state, expressed as percent the parent compound, appear to be significantly different in patients on single and combined drug therapy.

Surface enhanced resonance Raman study of phenobarbital-induced rabbit liver cytochrome P-450 LM2.

Surface enhanced resonance Raman (SERR) spectroscopy has been used to study the vibrational spectra of the heme of purified rabbit liver cytochrome P-450 LM2 which was adsorbed on colloidal silver suspensions or on a silver electrode. Bases on a comparison with the resonance Raman (RR) spectra of the 'solute' species the high sensitivity of the SERR technique is demonstrated. Two different features were chosen in order to determine the structural and functional integrity of the adsorbed P-450. Both, substrate-induced spin state changes on the oxidized P-450 and the effect of the thiolate ligand on the oxidation state marker band v4 in the reduced P-450 could be observed in the SERR spectra of the adsorbed as well as in the RR spectra of the dissolved enzyme. These findings indicate that the protein structure near the substrate binding site and the coordination by thiolate are not affected by the interaction with the metal surface. Both structural elements are crucial for the function of P-450. Thus the elementary processes of the enzymatic action of P-450 can be investigated by this highly sensitive version of RR spectroscopy.

Immunodeficiency, xanthomas and obstructive liver disease.

Chronic obstructive liver disease and secondary hyperlipidemia developed in an immunodeficient boy. Sequential addition of cholestyramine and phenobarbital to his medical regimen, following an initial response to bile drainage, resulted in the disappearance of xanthomas and pruritus, and the restoration of normal serum concentrations of lipids and bile acids. This improvement may result from shifting the bile acid pool from the peripheral blood compartment to the enterohepatic circulation.

Quantitative immunocytochemical analysis of the induction of cytochrome P450IIB in rat hepatocytes.

We examined whether induction of the phenobarbital (PB)-inducible form of cytochrome P450 (P450IIB) in rat hepatocytes could be analyzed quantitatively by immunogold electron microscopy. Rats received intraperitoneal injections of PB every 24 hr and livers at the various stages of PB induction were fixed by perfusion with a mixture of paraformaldehyde (4%) and glutaraldehyde (0.1%) and embedded in LR White. Ultra-thin sections were cut and labeled by the protein A-gold procedure using affinity-purified anti-P450IIB antibody which was previously immunoabsorbed with liver microsomes from a control rat (not treated with PB). We counted the number of gold particles per micron of the rough ER membranes (particle density). Before PB treatment, the particle density of the rough ER in rat hepatocytes was practically zero and increased markedly at 48 and 72 hr after PB treatment. The rough microsomes were prepared from these PB-treated rat livers. The amount of P450IIB was estimated by immunoblot analysis and the number of gold particles bound to the rough microsomal membrane was determined by the same post-embedding immunogold procedure. The particle density of the rough microsomes increased in parallel with the increase in the amount of P450IIB, indicating good correlation of the two variables. Thus, the induction of cytochrome P450IIB can be quantitatively and reliably investigated by immunogold electron microscopy.

Effect of cytochrome P-450 inhibition and stimulation on intensity of polyethylene degradation in microsomal fraction of mouse and rat livers.

Polyethylene (PE) is degraded in microsomal fractions of mouse and rat livers with the formation of carbonyl groups. Infrared spectroscopy demonstrated formation of predominantly ketone groups and to a lesser degree ester and aldehyde groups. The inhibition and stimulation of cytochrome P-450 in mouse livers affected the formation of oxidative groups on PE. Phenobarbital doses of 3 x 0.05 mg per mouse increased the concentration of cytochrome P-450 and ketone groups on PE, whereas the vaccine Propionibacterium acnes (0.5 mg) and its pyridine fraction (0.5 and 1 mg) had the opposite effect. The coherence of cytochrome P-450 with oxidative changes on PE is compared and discussed with findings on implants in man.

Pentobarbital sodium and attack behavior in male Siamese fighting fish.

An experiment was undertaken to determine the effects of pentobarbital sodium on intraspecific attack behavior in male Siamese fighting fish in an attempt to extend earlier findings with chlordiazepoxide and secobarbital sodium. Pairs of fish fought while immersed in 20 microgram/ml or 40 microgram/ml pentobarbital sodium or plain water. The 40 microgram/ml group showed significantly less attack (e.g., biting, jaw locking) than either control or low dose groups without producing a change in general arousal. Quasisexual behavior, seen in an earlier chlordiazepoxide study, did not occur in the present study.

Serum squalene levels in hepatobiliary diseases.

Serum squalene levels did not change in patients with acute hepatitis, chronic active hepatitis and liver cirrhosis, but were significantly reduced in patients with intra- and extrahepatic cholestasis. The ratio of cholesterol to squalene remained normal in patients with acute hepatitis as well as chronic active hepatitis, while being slightly decreased in patients with liver cirrhosis. On the other hand, in patients with cholestasis the ratio was markedly raised. From these observations we confirmed abnormal sterol metabolism in hepatobiliary diseases, and clinical usefulness of the ratio of cholesterol to squalene to distinguish hepatocellular injury and cholestasis.

A non-invasive method for the study of hepatic drug metabolism in rodents: antineoplastic drug effects on antipyrine metabolism in mice.

A rapid, sensitive and simple high pressure liquid chromatography (HPLC) method is described for the direct analysis of antipyrine in saliva. The detection limit was found to be 1.0 ng/ml of sample, lower than any previously reported method. Accuracy and precision were maintained with as little as 0.5 microliter of saliva. Thus the rate of elimination of antipyrine has been monitored non-invasively in rats and for the first time in mice. The antipyrine half-life was found to be 28.9 +/- 4.0 (S.E.M.) min and 111 +/- 20 min in mice and rats, respectively. In mice single i.p. doses of 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU) (30 mg/kg) produced increases in antipyrine half-life, up to 28 days post-treatment. The maximum effect of BCNU was observed on day 7 with an antipyrine half-life of 74.4 +/- 15.7 min. Phenobarbital induction lowered the antipyrine half-life in controls to 12.6 +/- 1.2 min. An enhanced inductive effect was observed in BCNU-treated mice: BCNU-treated, phenobarbital-induced mice displayed a half-life for antipyrine of 7.4 +/- 0.6 min on day 21 post BCNU dose. These effects could not be attributed to changes in absorption of antipyrine in BCNU-treated mice.