Dose dependent suppression of hepatic cytochrome P-450 content by doxorubicin and Mitomycin-C: correlation with antipyrine biotransformation

Synergism antibacterial activity for novel synthesized Schiff base ligands and semi-thiosemicarbazones with ß-diketones and 4-aminoantipyrine

Schiff base ligands were synthesised in this work, the first is (Z)-2-((Z)-3-((1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)imino)-1,3-diphenylpropylidene) hydrazine-1-carboxamide, the second is (Z)-2-((1E,5Z,6E)-5-((1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)imino)-1,7-bis(4-hydroxy-3-methoxyphenyl)hepta-1,6-dien-3-ylidene)hydrazine-1-carbothioamide. The Schiff base ligands both were synthesised using the same method (the single pot reaction), using EtOH as the reaction medium and GAA as the catalyst in fixed temperature at 70 0C and reflux for 6 hrs. The starting materials of HL1 were semicarbazide,4-aminoantipyrine and dibenzoyl methane, while the starting materials of HL2 were TSC, 4-AAP and Curcumin. The ligands proved to be bi-dentate ligands that coordinate from the azomethane groups. FT-IR, U.V-Visible, 1H and 13C- NMR, molar conductivity, and magnetic susceptibility were used to identify all the compounds produced. The metal ions used in preparing the complexes in this work were Co(II), Cu(II) and Cr(III). Schiff base and its complexes were evaluated for antibacterial activity against four bacterial strains of Gram-negative (Escherichia coli and Pseudomonas aeruginosa), Gram-positive (Staphylococcus aureus and Bacillus Subtilis) and two types of fungi (Candida albicans and Rhizopus Sporium), the results were positive for all compounds tested. Keywords: Schiff base, Curcumin, 4-aminoantipyrine

[Microsomal oxidative metabolism in the liver of rats treated with vinorelbine: evaluation through antipyrine elimination]

BACKGROUND

Determination of the metabolic efficiency of the liver in neoplastic diseases in patients receiving highly toxic drugs is of great practical importance.

METHODS

The effect of vinorelbine on the metabolic efficiency of the liver was evaluated by means of phenazone kinetics in rats. The test was compared with a battery of tests routinely used whenever hepatic dysfunction is suspected.

RESULTS

Vinorelbine was administered to the rats and the pharmacokinetic parameters of antipyrine were compared with those in control rats. A statistically significant prolongation of the elimination half-life, as well as a decrease in the elimination constant and clearance of antipyrine were found in the rats receiving the anticancer drug in comparison with controls (p < 0.01). Statistically significant correlations were found between the elimination half-life of antipyrine and serum albumin values (p < 0.01) and prothrombin time (p < 0.001).

CONCLUSIONS

Determination of antipyrine pharmacokinetics allows early detection of vinorelbine-induced hepatic dysfunction, with a sensitive scale.

Lack of mechanism-based inactivation of rat hepatic microsomal cytochromes P450 by doxorubicin

Administration of the antineoplastic doxorubicin to rodents causes depression of hepatic cytochrome P450 (CYP) dependent biotransformation, an effect that has been partially attributed to the ability of doxorubicin to stimulate microsomal lipid peroxidation. Since doxorubicin can be bioactivated by the CYP/NADPH-CYP reductase system to products that bind covalently to microsomal protein, we hypothesized that doxorubicin functions as a mechanism-based inactivator of hepatic microsomal CYPs and (or) NADPH-CYP reductase under conditions in which doxorubicin-stimulated NADPH-dependent lipid peroxidation is minimized. In vitro studies were conducted with hepatic microsomes isolated from untreated and phenobarbital-treated male rats. Unlike the positive control carbon tetrachloride, doxorubicin (10 µM) did not stimulate NADPH-dependent lipid peroxidation in microsomal incubations containing EDTA (1.5 mM). Doxorubicin did not cause NADPH-dependent loss of microsomal CYP, heme, or steroid hydroxylation activities selective for CYP2A, CYP2B, CYP2C11, and CYP3A. The positive control 1-aminobenzotriazole caused marked NADPH-dependent decreases in all of these parameters. Neither doxorubicin nor 1-aminobenzotriazole caused NADPH-dependent loss of NADPH-CYP reductase activity, and neither compound altered the immunoreactive protein levels of CYP2B, CYP2C11, CYP3A, and NADPH-CYP reductase. These results indicate that a pharmacologically relevant concentration of doxorubicin does not cause direct mechanism-based inactivation of hepatic microsomal CYPs or NADPH-CYP reductase, suggesting that the ability of doxorubicin to depress hepatic CYP-mediated biotransformation in vivo is due to lipid peroxidation mediated heme destruction, altered heme metabolism, and (or) decreased expression of selected CYP enzymes.Key words: doxorubicin, cytochrome P450, mechanism-based inactivation, lipid peroxidation.

Effects of cyclophosphamide and adriamycin on rat hepatic microsomal glucuronidation and lipid peroxidation

The effect of cytotoxic drug administration, as a single dose i.p. to rats (six rats/treatment group), on hepatic microsomal UDP-glucuronosyltransferase (UGT) activity was investigated. Glucuronidation of morphine in microsomes from control rats apparently involved at least two enzymes. Administration of cyclophosphamide (CP; 200 mg/kg 7 days prior to killing) significantly increased the rate of morphine glucuronidation over the range 0.05-10 mM, and significantly increased the apparent Vmax for the high capacity isoenzyme from 1.25 +/- 0.12 to 1.95 +/- 0.39 nmol/mg/min. In contrast, the activity of 1-naphthol UGT was not significantly altered by administration of CP. Rats treated with the same dose of CP 1 day prior to killing showed a significant decrease in microsomal morphine-UGT activity at 0.05 and 2.5 mM morphine, but a significant increase in activity was observed following administration of CP or Adriamycin (AD; 10 mg/kg) 4 days prior to killing. The extent of microsomal lipid peroxidation was significantly increased in microsomes obtained from rats treated with CP or AD 4 days prior to killing, and was positively correlated (P less than 0.001) with the rate of glucuronidation of 0.05 and 2.5 mM morphine. Preincubation of microsomes in the presence of CP (5 mM) and AD (100 microM) significantly decreased the rate of glucuronidation of 2.5 mM morphine. In vitro NADPH-mediated lipid peroxidation significantly increased the activity of both the high and low affinity morphine-UGT isoenzymes. Administration of the cytotoxic drugs CP and AD may alter microsomal morphine-UGT activity via the process of lipid peroxidation, although other mechanisms cannot be excluded.

The influence of antineoplastic chemotherapy on antipyrine metabolism in man

When either Doxorubicin or Mitomycin-C was administered to patients, antipyrine clearance was respectively unaltered or increased. Antipyrine was administered to patients two days prior to and one day after their first course of the chemotherapeutic drug. Antipyrine clearance increased an average of 11.2% in the 5 patients that received Doxorubicin (not significant) and 15.2% in the six patients that received Mitomycin-C (P = 0.033, students t-test). The altered clearance is likely due to a rapid induction of the mixed function oxidase system by the chemotherapy as other parameters that could influence clearance were stable throughout the study (volume of distribution, weight, creatinine clearance and liver function tests). It is unlikely that the prechemotherapy antipyrine dose accounted for this change. The administration of these two antitumor antibiotics in humans may modestly increase the mixed function oxidase activity that is responsible for the metabolism of antipyrine. These findings are in direct contrast to markedly decreased mixed-function oxidase activity observed in the rodent pretreated with the same chemotherapy.