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D R Petersen

Publications and source records attributed to D R Petersen.

79 records · Page 5Linked to original sources
PubMedDate not supplied

Characterization of brain acetaldehyde oxidizing systems in the mouse.

C57BL mice were treated (75 or 100 mg/kg) with pargyline or Lilly 51641 90 min prior to sacrifice. Liver and brain subcellular fractionation revealed that pretreatment with these drugs resulted in a significant inhibition of aldehyde dehydrogenase (ALDH) in liver cytosol and mitochondria, while brain ALDH in these same fractions was unaffected. Administration of pargyline or Lilly 51641 prior to ethanol treatment (3.0 g/kg) resulted in a significant elevation of blood acetaldehyde. Significant increases in brain acetaldehyde concentrations were not observed until blood acetaldehyde levels surpassed 200 nmol/ml. When mice were injected with ethanol (3.0 g/kg) and acetaldehyde (200 mg/kg), a similar relationship between blood and brain acetaldehyde concentrations was observed. Data presented in the present study indicate that there are very efficient enzymatic mechanisms responsible for acetaldehyde oxidation in brain and that at blood acetaldehyde concentratins normally occurring after ethanol ingestion, brain acetaldehyde levels would be extremely low.

Acetaldehyde↗
PubMedDate not supplied

Aldehyde dehydrogenase and aldehyde reductase in isolated bovine brain microvessels.

The activities of aldehyde dehydrogenase and aldehyde reductase were measured in microvessel fractions isolated from bovine brain. Aldehyde dehydrogenase specific activity in microvessels was enriched 1.5-fold over that measured in grey matter. The specific activity of aldehyde reductase was significantly lower in parenchymal vessles and microvessels than in grey matter. The presence of aldehyde dehydrogenase and aldehyde reductase in cerebral microvasculature is consistent with previous reports of enrichment of other enzymes involved in synthesis and degradation of monoamines. The enrichment of aldehyde dehydrogenase in cerebral microvasculature provides additional evidence for an enzymatic blood-brain barrier for biogenic aldehydes or ethanol-derived acetaldehyde.

Acetaldehyde↗
PubMedDate not supplied

Pharmacokinetic analysis of the metabolism of cocaine to norcocaine and N-hydroxynorcocaine in mice.

Cocaine is hepatotoxic in humans and is a very effective hepatotoxin in the mouse. Previous in vitro studies have shown that the mixed function oxidase system is very important in the metabolism of cocaine to the hepatotoxic species. Activation of cocaine to the cytotoxic species is thought to proceed through the N-demethylation and subsequent N-hydroxylation of the bridgehead amine. The in vivo metabolism of cocaine involves not only oxidative but also hydrolytic mechanisms. Therefore the principle aim of this study was to establish a system in which the in vivo metabolism of cocaine to norcocaine and N-hydroxynorcocaine could be determined. The in vivo metabolism of acutely administered cocaine to norcocaine and N-hydroxynorcocaine was assessed in two inbred mouse strains; one that is relatively sensitive to cocaine hepatotoxicity but shows little enhancement in toxicity when pretreated with phenobarbital (DBA/2lbg), and one that shows little hepatotoxicity unless pretreated with phenobarbital (C57BL/6lbg). Although no significant differences between the strains were seen in the pharmacokinetics of cocaine, the half-life of both norcocaine and N-hydroxynorcocaine was significantly longer in DBA mice. Accordingly, the area under the curve values for hepatic norcocaine and N-hydroxynorcocaine were approximately 5- and 3-fold greater, respectively, in DBA as compared with C57BL mice. The higher levels of both norcocaine and N-hydroxynorcocaine in the DBA mouse are consistent with previously established differences in cocaine hepatotoxicity in these strains of mice. Pretreatment of C57BL mice with phenobarbital prolonged the half-life of norcocaine and N-hydroxynorcocaine 5- to 8-fold over C57BL control values.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

The metabolism of 3,7-dimethyl-2,6-octadienal (citral) in rat hepatic mitochondrial and cytosolic fractions. Interactions with aldehyde and alcohol dehydrogenases.

Citral (3,7-dimethyl-2,6-octadienal), a flavoring and fragrance agent, is associated with a variety of biochemical and toxicological effects. Reports of the in vivo metabolism of citral suggest that a primary route of metabolism is conversion to the corresponding acid species presumably by aldehyde dehydrogenases (ALDH). In the present study, hepatic mitochondrial and cytosolic fractions were prepared from male Sprague-Dawley rats to assess in vitro metabolism of citral. Evidence of ALDH-mediated citral oxidation was not seen in either subcellular fraction. On the contrary, citral was found to be a potent inhibitor of acetaldehyde oxidation by the low-KM mitochondrial form of ALDH. Measurement of the in vitro acetaldehyde oxidation rates of this isozyme in the presence of citral lead to the estimation of a Ki of 360 nM. Further studies of citral effects on low-KM mitochondrial ALDH indicate that inhibition is by a linear mixed-type mechanism and does not involve citral binding at the NAD+ binding site. In addition, it was observed that citral was readily reduced to the corresponding alcohol by alcohol dehydrogenase (ADH) in the cytosolic fraction. The reduction of citral in the presence of NADH proceeded at two distinct rates; an initial "fast" rate followed by a "slow" rate. Individual kinetic constants were calculated for the two rates. It is possible that the differential ADH-mediated reduction rates of citral are the result of varying affinities for the enzyme of the two citral isomers, geranial (trans) and neral (cis).(ABSTRACT TRUNCATED AT 250 WORDS)

Acyclic Monoterpenes↗
PubMedDate not supplied

Inhibition of rat liver aldehyde dehydrogenases by acrolein.

Acrolein, the lowest member of the ethylenic aldehyde series, has been widely studied as a result of the diverse toxicities associated with it. Previous investigations into the enzymatic process responsible for the detoxification of acrolein implicated rat liver aldehyde dehydrogenase (ALDH) in the oxidation of this aldehyde. Contrary to these reports, in our investigation we were unable to detect the oxidation of acrolein to acrylic acid by Sprague-Dawley rat liver mitochondrial or cytosolic ALDHs measured spectrophotometrically by the production of NADH, or by HPLC analysis for the production of acrylic acid. However, in the course of these experiments, it was demonstrated that acrolein is a potent inhibitor of rat liver ALDHs. Mitochondrial and cytosolic high affinity ALDHs are particularly sensitive to the inhibitory effects of acrolein. The type of inhibition exhibited by these high affinity ALDHs is primarily irreversible, with a slight degree of reversible noncompetitive inhibition. The inhibition is rapid with a 91 and 33% reduction in control mitochondrial and cytosolic ALDH activities, respectively, with a 5-sec preincubation of 30 microM acrolein prior to the addition of the aldehyde substrate. Significant inhibition of total (high plus low affinity isozymes) mitochondrial and cytosolic ALDHs occurs only at relatively high acrolein concentrations (greater than or equal to 50 microM). The inhibition displayed by the total mitochondrial and cytosolic ALDHs is mixed-type, with both reversible noncompetitive and irreversible inhibition demonstrated.

Acrolein↗
PubMedDate not supplied

A comparative study of the disposition of nicotine and its metabolites in three inbred strains of mice.

The disposition of nicotine, cotinine, and nicotine N-oxide was investigated in male C57BL, DBA, and C3H mice following an ip injection of nicotine (1.0 mg/ml). The half-lives (t1/2) of nicotine in blood were 5.9 to 6.9 min. The rapid elimination of nicotine was accompanied by a rapid accumulation of metabolites; maximal concentrations of cotinine in blood (204 to 364 ng/ml) were achieved in 10 min and nicotine N-oxide (23 ng/ml in C3H mice) in 15 min. The t1/2 in blood was 20.1 to 39.8 min for cotinine and 18.4 min for nicotine N-oxide. The t1/2 values for nicotine in brain were similar to those in blood, but the values for liver were slightly larger (6.3 to 9.2 min) and interstrain differences were significant. A large strain-related difference in the t1/2 for cotinine was found; the metabolite was eliminated from the blood of DBA mice at only about one-half the rate determined for the other strains. The t1/2 for nicotine N-oxide in liver ranged from 12.7 to 27.3 min; the values were significantly different with C57BL greater than DBA greater than C3H. Strain-related differences were also observed in response to chronic exposure to cigarette smoke. The t1/2 of injected nicotine appeared to be slightly decreased in C57BL and DBA mice but was increased by 60% in livers of C3H mice compared to a control group.

Animals↗