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11 recordsLinked to original sources
PubMed1976

Factors affecting the excretion of 14C-dicumarol in the bile of rats.

1. After i.v. injection of equivalent doses of 14C-dicumarol, male rats excreted about 2 1/2 times more radioactivity in bile (9.3 +/- 0.7% in 2 hr) than did females (3.9 +/- 0.4% in 2 hr). 2. Exogenous agents: while 24 hr pretreatment with benzpyrene or 3-methylcholanthrene did not alter the excretion of 14C-dicumarol and its metabolities in bile, pretreatment with carbon tetrachloride reduced radioactivity in the bile of male rats 60%. Following single rapid injection of sulfobromphthalein (BSP), the radioactivity in bile, decreased 70%. 3. Most of the radioactivity in bile (80-90%) was present in metabolized form regardless of the dose, the sex of the rat, or the exogenous agent used.

Animals↗
PubMed1975

Determination of dicumarol metabolites in bile of rats.

After intravenous administration of dicumarol-14C to rats, the bile excreted over the next 24 hr contained from 32 to 46% of the administered radioactivity. At least three primary metabolites and a small amount of unchanged dicumarol were present in the bile. Over 91% of the primary metabolites was converted to dicumarol and 7-hydroxydicumarol by hydrolysis with beta-glucuronidase. Some primary metabolites were hydrolyzed simply by acidification to pH 3 or by treatment under the acidic conditions utilized in the enzymatic hydrolysis. The three primary metabolites contain carboxylic acid groups, as indicated by their electrophoretic mobility-pH profiles, and some are simple glucuronides of dicumarol and 7-hydroxydicumarol. The possibility that others are derivatives of these compounds in which a coumarin lactone ring is opened cannot be ruled out. When the metabolites released by either acidification or enzymatic hydrolysis were chromatographed in n-butanol-3 M ammonia, artifacts were produced, presumably as a result of decomposition of 7-hydroxydicumarol. The question is raised whether a previously reported metabolite (B055) is an artifact.

Animals↗
PubMed1991

Isolation, identification, and assay of [3H]-porfiromycin adducts of EMT6 mouse mammary tumor cell DNA: effects of hypoxia and dicumarol on adduct patterns.

[3H]-(N-la-methyl) Porfiromycin (POR) was employed to detect and identify the radiolabeled mono- and bis-adducts formed in living EMT6 mouse mammary tumor cells under different conditions. To provide authentic standard adducts, calf-thymus DNA was treated with POR under reductive activation, then digested to nucleosides and POR-nucleoside adducts. The three major adducts formed were isolated by HPLC and authenticated. Two were mono-adducts, composed of deoxyguanosine linked at its N2-position to C-1 of POR and of 10-decarbamoyl POR. The third was a bis-adduct, in which POR was crosslinked to two deoxyguanosines at their N2-positions. DNA from [3H]-POR treated EMT6 cells was digested an analyzed by HPLC. DNA-associated label was located in thymidine and in two mono-adducts and one bis-adduct identical to those described above. Label in thymidine resulted from N-demethylation of POR and reincorporation of label into new thymidylate residues. Adducts were formed more abundantly in hypoxia than in air. In addition, the mono-adduct to crosslink ratios were different, approximately 1:1 and 2:1 for hypoxic and aerobic cells, respectively. The different patterns of alkylation in air and hypoxia may be related to the greater toxicity of POR in hypoxia. When cells were treated simultaneously with POR and dicumarol, adduct levels were lower, and a new, unknown adduct was observed primarily under hypoxia; these changes may be related to the altered toxicity of POR in the presence of dicumarol. The HPLC assay detected simultaneously the full array of stable mono- and bis-adducts in DNA with good sensitivity (greater than or equal to 2 x 10(6) adducts/nucleotide) and excellent reproducibility. This assay should be generally applicable to all cells and tissues when MC or POR with high specific radioactivity can be employed.

Alkylation↗
PubMed1987

Reduction of irreversible binding of diethylstilbestrol in hamster renal cortex by inhibitors of cytochrome P-450.

Hamster renal cortical slices metabolized [3H]diethylstilbestrol (DES) to reactive intermediates that irreversibly bound to macromolecules. Protein isolated from cortical slices following incubation with 50 nM [3H]DES for 90 min at 37 degrees C had 0.160 pmol [3H]DES eq/mg protein irreversibly bound. Samples of protein analyzed by gel electrophoresis revealed several radioactive peaks, indicating that specific adduct formation had occurred. No radioactivity was associated with DNA isolated from the same tissue slices. Incubation of the slices with [3H]DES under an atmosphere enriched in carbon monoxide decreased the nonextractable binding of [3H]DES metabolites to protein. The cytochrome P-450 inhibitors diethylaminoethyl 2,2-diphenylpentanoate HCl (SKF 525-A), metyrapone, butylated hydroxytoluene (BHT), and dicumarol decreased the irreversible binding of [3H]DES by 38 to 72%. Analysis of metabolites isolated from the incubation medium by high-pressure liquid chromatography indicated that carbon monoxide, BHT, and dicumarol inhibited the hydroxylation of [3H]DES. Arachidonic acid and indomethacin did not alter the irreversible binding of [3H]DES, indicating a lack of involvement of prostaglandin H synthetase in the metabolism of DES to reactive intermediates. These findings suggest that cytochrome P-450 isozymes in the hamster renal cortex metabolize DES to reactive species that covalently bind to macromolecules.

Animals↗
PubMed1977

Actions of insulin in fat cells. Effects of low temperature, uncouplers of oxidative phosphorylation, and respiratory inhibitors.

When isolated rat epididymal fat cells were incubated with [125I]iodoinsulin for 5 min at 37 degrees, radioactivity accumulated in the plasma membrane fraction (Peak 1) and an unidentified particulate fraction (Peak 2) as reported previously (Kono, T., Robinson, F.W., and Sarver, J.A. (1975) J. Biol. Chem. 250, 7826-7835). This accumulation of radioactivity in Peak 2 (but not that in Peak 1) was greatly impaired when cells were incubated with iodoinsulin in the presence of a variety of metabolic inhibitors that reduce the cellular content of ATP. The reduction in the ATP level coincided with a disappearance of the stimulatory effects of insulin on sugar transport and the hormone-sensitive phosphodiesterase. In contrast, ATP depletion had no significant effects, at least during a 5-to 15-min incubation, on the intracellular water space and on the basal sugar transport and phosphodiesterase activities. When cells once depleted on ATP by treatment with 2,4-dinitrophenol (1 mM; 10 min) were washed and suspended in fresh buffer, the ATP level was recovered almost fully in 10 min. This recovery coincided with the restoration of responsiveness to insulin. When cells were incubated with [125I]iodoinsulin or insulin for 5 min at 15 degrees instead of 37 degrees, a negligible quantity of radioactivity accumulated in Peak 2 and insulin failed to activate sugar transport. In contrast, under the same conditions, radioactivity accumulated in Peak 1 and insulin stimulated phosphodiesterase considerably. These results suggest that ATP, or some other compound metabolically related to ATP, may be necessary for the actions of insulin on sugar transport and phosphodiesterase. ATP, or some other related compound, may also be necessary in the formation of the radioactive Peak 2, although the physiological function and cellular location of this peak are yet to be ascertained.

Acetylglucosaminidase↗
PubMed1973

The effect of salicylate on the biliary excretion of 14C-bishydroxycoumarin in rat.

1. The effect of intravenous sodium salicylate on the biliary excretion of 14C-bishydroxycoumarin ((14)C-BHC) was studied in rats.2. Salicylate (88.9 mg/kg) increased the biliary excretion of (14)C-radioactivity from a control value of 12.3 +/- 2.7% to 29.3 +/- 2.5% of the administered dose in 6 h after injection.3. During the 6 h period, 11% of the dose of radioactivity underwent biliary recycling in the salicylate-treated rats compared to only 6% in the absence of salicylate.4. About 15.3% of the radioactivity excreted in the bile of rats given BHC alone was detected as unchanged BHC, 8.6% was present as BHC-conjugate, conjugates of BHC metabolites accounted for 30.9%, and the remainder consisted of unidentified metabolites.5. Salicylate treatment did not significantly alter the excretory pattern of unchanged BHC and its metabolites.

Animals↗
PubMed1969

The effect of inhibitors on the formation of phosphoenolpyruvate by rat liver mitochondria.

1. Rat liver mitochondria oxidizing malate produce PEP (phosphoenolpyruvate) without the addition of ATP or other nucleotides. 2. The addition of oligomycin in the presence of 2,4-dinitrophenol did not abolish PEP formation and in some instances stimulated its formation. 3. Formation of PEP was inhibited by arsenate. 4. Arsenite decreased PEP formation and caused accumulation of pyruvate. 5. Added GTP and ITP had no effect on PEP formation. 6. PEP formed from malate in the presence of GTP and labelled P(i) had a specific radioactivity approximately the same as the P(i) with no contribution from the phosphate of the added GTP. 7. There was no parallelism between the effects of inhibitors on PEP formation from malate and their effects on the assayed activity of PEP carboxykinase. 8. In a direct comparison it was shown that the PEP carboxykinase content of mitochondria was insufficient to account for the PEP formation from malate. 9. Consideration of the kinetic characteristics of PEP carboxykinase and mitochondrial content of oxaloacetate and GTP show that this enzyme cannot account for the PEP formed from malate by mitochondria.

Adenosine Triphosphate↗
PubMed1988

Location of gamma-carboxyglutamyl residues in partially carboxylated prothrombin preparations.

Prothrombin contains 10 gamma-carboxyglutamyl (Gla) residues in the N-terminal (fragment 1) domain of the protein. Following anticoagulant administration, a spectrum of undercarboxylated, physiologically less active forms of prothrombin is secreted into bovine or human plasma. The sites of undercarboxylation in these prothrombin species have now been investigated. Plasma containing a mixture of partially carboxylated forms of prothombin was obtained from a dicoumarol-treated bovine, and three pools of partially carboxylated (four, six, or eight Gla) species were purified by adsorption onto barium citrate and barium oxalate, ammonium sulfate fractionation, and chromatography. Fragment 1 obtained from these variants was equilibrated with 3H2O and heated in a dry state to decarboxylate Gla and incorporate 3H into the resulting Glu residues. This peptide was then sequenced by Edman degradation, and the specific radioactivity of PTH-Glu was determined for each potential Gla-containing site. Data obtained from normal prothrombin fragment 1 fit a linear model when the log of specific activity of PTH-Glu was plotted against the cycle number. Analysis of the 80% variant showed a decrease in carboxylation only in the last two Gla residues, while data obtained from the 60% variant indicated a general decrease in carboxylation from the most amino- to the more carboxyl-terminal Gla residues. In the 40% Gla variant, all but the most amino-terminal of the Gla residues appeared to be undercarboxylated. These data indicate that the gamma-carboxylation of glutamyl residues in prothrombin does not occur randomly but instead with preferential carboxylation of the most amino-terminal Gla residues. When carboxylation is limited, the impairment of carboxylation is more severe at the more carboxyl-terminal residues.

1-Carboxyglutamic Acid↗