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Biomedical subjects

J A Menzies

Publications and source records attributed to J A Menzies.

At least 19 recordsLinked to original sources
PubMed1999

Detection of quantitative trait loci affecting caffeine metabolism by interval mapping in a genome-wide scan of C3H/HeJ x APN F(2) mice.

Caffeine metabolite ratios have been widely used to measure cytochrome P-450 1A2 activity in humans. Serum paraxanthine/caffeine ratio is one such index of this activity. We had previously demonstrated genetic variation of this trait among inbred mouse strains. In the present study, we have undertaken a genome-wide scan for quantitative trait loci affecting this trait with an interval mapping approach on an F(2) intercross population of acetaminophen nonsusceptible and C3H/HeJ inbred mice. A statistically significant association (log-likelihood ratio = 25.0) between a locus on chromosome 9, which colocalized with the murine Cyp1a2 locus, and the plasma paraxanthine/caffeine ratio was identified. This result suggested the presence of an expression polymorphism affecting this gene. A second locus was identified on chromosome 1 (log-likelihood ratio = 9.7) for which no obvious candidate gene has been identified. The influence of this locus on the paraxanthine/caffeine index was more significant among males (log-likelihood ratio = 6.3) than females (log-likelihood ratio = 3.6). A third locus was identified on chromosome 4 with a less statistically robust association (log-likelihood ratio = 3.4) to the paraxanthine/caffeine phenotype. Collectively, these three loci accounted for 63.2% of the variation observed in the F(2) population for this phenotype. These results demonstrate the potential for genetic variation arising from factors other than CYP1A2 activity to influence the plasma paraxanthine/caffeine ratio in mice. This study demonstrates the utility of quantitative genetics in the analysis of polygenic drug metabolism.

Animals↗
PubMed1997

Differences in caffeine 3-demethylation activity among inbred mouse strains: a comparison of hepatic Cyp1a2 gene expression between two inbred strains.

The 3-demethylation of caffeine can be used as an index of cytochrome P450 CYP1A2 activity in vivo. We compared the plasma levels of caffeine and the 3-demethylated metabolite. 1,7-dimethylxanthine, in six common inbred strains (A/J, P/J, BALB/cJ, C3H/HeJ, AKR/J, and SWR/J) and one inbred strain (APN) derived in our laboratory from outbred Swiss-Webster mice on the basis of its relative susceptibility to acetaminophen-induced hepatotoxicity. We found significant variations between a number of the common strains, all of which produced significantly higher caffeine 3-demethylation indices than our APN strain. In three of the six common strains, there was a significant difference between males and females, with the females having consistently lower 1,7-xanthine/caffeine ratios. Hepatic Cyp1a2 expression was compared between APN and C3H/HeJ males. Microsomal methoxyresorufin O-demethylation, acetanilide 4-hydroxylation, and CYP1A2 immunoreactive protein levels were significantly higher in C3H/HeJ relative to APN mice, as were hepatic CYP1A2 mRNA levels. These results indicate the importance of strain and gender to the outcome of pharmacological or toxicological studies involving CYP1A2-mediated metabolism, as well as the suitability of the plasma 1,7-dimethylxanthine/caffeine ratio as a marker of CYP1A2 activity in the mouse. The striking differences observed between the APN and C3H/HeJ mice suggest that these strains may be suitable for a genetic analysis of the regulation of the basal expression of CYP1A2, a key enzyme in procarcinogen activation.

Acetaminophen↗
PubMed1997

Increased basal expression of hepatic Cyp1a1 and Cyp1a2 genes in inbred mice selected for susceptibility to acetaminophen-induced hepatotoxicity.

Susceptibility to acetaminophen-induced hepatotoxicity was found to vary widely in an outbred colony of Swiss Webster mice. Some acetaminophen-treated male mice showed a significant elevation in serum levels of the hepatic enzyme alanine aminotransferase at a normally non-hepatotoxic oral dose. A selective breeding program over 17 generations produced inbred mice which were either susceptible or nonsusceptible to the hepatotoxic effects of acetaminophen. Liver microsomes from the susceptible group showed a statistically significant increase in the ability to metabolize acetaminophen to a reactive intermediate which covalently binds N-acetylcysteine. Microsomal cytochrome P450 activities associated with CYP1A2 (acetanilide 4-hydroxylation and methoxyresorufin O-demethylase) were significantly increased in the susceptible group. Ethoxyresorufin O-deethylase activity, associated with both CYP1A1 and CYP1A2, was also significantly elevated in this group. Further examination of both CYP1A isoforms revealed that hepatic CYP1A1 and CYP1A2 mRNA and protein levels were significantly elevated in animals from the susceptible group. In vivo caffeine 3-demethylation, which is associated with CYP1A2 activity, co-segregated with acetaminophen susceptibility and showed a significant positive correlation (r = 0.626, p < 0.005) with CYP1A2 mRNA expression in animals from both the susceptible and nonsusceptible groups. The co-segregation of elevated basal Cyp1a1 and CYP1a2 gene expression levels in animals selected for susceptibility to acetaminophen-induced hepatotoxicity suggested a common heritable basis for regulation of basal expression of both of these CYP1A isoforms. This was supported by the correlated expression of both CYP1A mRNAs within individual mice (r = 0.644, p < 0.02).

Acetaminophen↗
PubMed1994

Reversed-phase LC assay method for deoxycholate in influenza vaccine.

Sodium deoxycholate is used for the disruption of particles in the manufacturing of some influenza vaccines. Residual deoxycholate in inactivated vaccines is currently determined using a labour-intensive colorimetric method which lacks complete specificity. An alternative assay method for residual deoxycholate in vaccine preparations was developed using reversed-phase LC. Cholic acid was used as internal standard and the ratio of internal standard to test solute was used for all calculations. Prior to LC analysis, deoxycholic acid was concentrated by solid-phase extraction, a procedure that also removed proteinaceous material in vaccine samples. The clean-up/concentration procedure recovery was examined using untreated samples and was found to be quantitative. The linearity range of the LC method was between 3 and 200 micrograms ml-1, with a limit of detection of approximately 0.4 micrograms on column, and a lower limit of quantitation of 1.6 micrograms on column. Replicate assays during intra-and inter-day experiments gave acceptable levels of variability. The DCA content of samples from three lots of influenza vaccine varied between 10 and 16 micrograms ml-1. These values were appreciably lower than those measured spectrophotometrically, indicating the higher specificity of the LC method.

Cholic Acid↗
PubMed1986

Inhibition of ovarian aromatase by ketoconazole.

In an in vitro system, ketoconazole inhibited the aromatization of [4-14C]-testosterone to estradiol-17 beta by rat ovarian tissue, in a dose-related manner. The amount of an intermediate, 4-androsten-17 beta, 19-diol-3-one, formed was also reduced. When the latter steroid or a subsequent intermediate, 4-androsten-19-aldehyde-3, 17-dione, was used as substrate, ketoconazole at approximately three times the molar concentration of the substrate, depressed estradiol-17 beta synthesis to 38% and 66% of control respectively. With ketoconazole in a concentration of about thirty times that of the substrate, estradiol-17 beta synthesis was depressed to approximately 10% that of control. It is concluded that ketoconazole inhibits all three sequential hydroxylation steps leading to the ovarian aromatization of androgens.

Animals↗
PubMed1986

Effect of single-dose ketoconazole on ovarian steroids.

The effect of the antifungal agent, ketoconazole, on rat ovarian concentration of progestins and androgens was investigated. A single oral dose of 20 mg/kg on the morning of proestrus resulted 3h later in a significant decrease. Control values at this time for progesterone, 17 alpha-hydroxyprogesterone, androstenedione and testosterone were 1173, 53, 40 and 2.5 ng/100 mg tissue respectively. In ketoconazole treated rats, the corresponding concentrations were 837, 34, 23 and 0.7 ng/100 mg tissue respectively. At a dose of 5 mg/kg ketoconazole, the concentrations of these steroids tended to be lower but the differences from control were not statistically significant.

Androgens↗
PubMed1985

Depression of ovarian estradiol-17 beta following single oral dose of ketoconazole.

Ketoconazole, administered as a single oral dose depressed ovarian concentration of estradiol-17 beta in rats. Estradiol-17 beta was quantitated, following dansylation, by a high-performance-liquid-chromatographic method. Control proestrous concentration was 111.2 +/- 6.9 pg/mg. With ketoconazole doses of 5 mg/kg and 20 mg/kg, the estrogen concentration was reduced to 84.0 +/- 8.4 pg/mg and 34.6 +/- 5.0 pg/mg respectively.

Administration, Oral↗
PubMed1984

Quantitation of delta 4-reduced metabolite of norethindrone in human plasma by HPLC-RIA.

An HPLC-RIA method for the measurement of the delta 4-reduced metabolite of norethindrone is described. The sensitivity of the method was such as to permit the quantitation of pg amounts (30 pg with an inter-assay CV of less than 7%). Nineteen volunteers received a single oral dose of 1 mg of norethindrone and, blood samples withdrawn at timed intervals, were pooled for each time period and assayed. The plasma concentrations of the dihydro metabolite ranged from 460 pg/ml at 30 min to 20 pg/ml at 24h.

Biotransformation↗
PubMed1983

HPLC-RIA of a metabolite of norethindrone in human plasma, 17 alpha-ethinyl-5 beta-estrane-3 alpha, 17 beta-diol, following conjugate hydrolysis.

An HPLC-RIA method for the assay of a reduced metabolite of norethindrone, 17 alpha-ethinyl-5 beta-estrane-3 alpha, 17 beta-diol, is described. Conjugated metabolites were extracted from human plasma and subjected to hydrolysis prior to analysis. With a daily dose of 2 mg of norethindrone, the mean plasma level of the metabolite was 24.8 ng/ml with a range of 22.8 ng/ml to 33.9 ng/ml.

Chromatography, High Pressure Liquid↗
PubMed1983

Norethindrone antisera: anomalous cross-reactivities with use of 3H-tetrahydro-reduced norethindrone as radioligand.

Anomalous cross-reactions with the dihydro- and tetrahydro-reduced metabolites of norethindrone were observed utilizing antisera raised against norethindrone-3-bovine serum albumin. Whereas displacement of 3H-norethindrone from the antiserum by the metabolites was generally minimal, where one of the metabolites was used as radiotracer, displacement by the metabolites was equal to or greater than that achieved by norethindrone. This unexpected finding was examined for its usefulness in developing a radioimmunoassay system for norethindrone metabolites in plasma. The sensitivity of the resulting standard curve was such as to permit quantitation of pg amounts of the reduced metabolites.

Animals↗
PubMed1981

An investigation of the interaction between isoniazid and the contraceptive steroid norethindrone in vivo.

Isonicotinic acid hydrazide (isoniazid) was shown to react readily with 17 alpha-ethinyl-17 beta-hydroxyestr-4-en-3-one (norethindrone) to form the isonicotinyl hydrazone of the steroid under conditions likely to exist in the stomach. The hydrazone was detected in guinea-pig, but not rat, plasma following its oral administration. Rat liver tissue metabolized the compound more rapidly than guinea-pig liver in vitro which probably accounts for the failure to detect the hydrazone in rat plasma.

Animals↗
PubMed1981

Identification of hydrazone of norethindrone, a metabolic product resulting from the interaction between isoniazid and norethindrone.

Co-administration of isonicotinic acid hydrazide (isoniazid, INH) and 17 alpha-ethinyl-17 beta-hydroxyestr-4-en-3-one (norethindrone, NE) resulted in the formation of the isonicotinyl hydrazone of norethindrone (INH-NE) in rat stomach. Rat liver metabolized the latter compound in vitro. The metabolic product was characterized, following its derivatization with p-methoxy-benzaldehyde (PMBA), by comparison of chromatographic and mass spectral properties with synthetic reference compound. Results showed that INH-NE was cleaved at the amide bond resulting in the formation of the hydrazone of norethindrone. The physicochemical characteristics of synthetic PMBA hydrazone of norethindrone are described.

Animals↗
PubMed1976

Biliary metabolites of estriol in the rat.

Following the subcutaneous administration of estriol-6,7-3H to rats, biliary metabolites were identified and quantitated. Approximately 70% of the metabolites were excreted in the form of "glucosiduronate" conjugates. 3,17beta-Dihydroxy-2-methoxy-1,3,5(10)-estratrien-16-one was the major metabolite in this conjugate fraction. Significant amounts of 3,17beta-dihydroxy-1,3,5(10)-estratrien-16-one and 2,3,17beta-trihydroxy-1,3,5(10)-estratrien-16-one, as well as smaller quantities of 1,3,5(10)-estratriene-2,316alpha,17beta, tetrol and 2-methoxy-1,3,5(10)-estratriene-3, 16alpha, 17beta-triol, were also found. In 17alpha-ethinylestradiol-treated animals, the rate of excretion of radioactivity and the proportion of 16-oxo-17beta-ol metabolites found in the "glucosiduronate" fraction were reduced.

Animals↗