Utjecaj progesterona na toksičnost benzena u štakora

Benzene is a frequently used industrial solvent. Its toxic manifestations could be modified by sex hormones, but mechanisms of their action are poorly understood. We have examined the influence of progesterone on lipid peroxidation (malondialdehyde), reduced glutathione (GSH), and cytochrome P450 2E1 (CYP2E1) in the liver and kidneys of female rats. Progesterone applied to benzene-treated rats inhibited the formation of reactive oxygen species (ROS), but in ovariectomised benzene-treated rats it significantly increased GSH in the liver. No improvement in CYP2E1 activity was observed in progesterone treated rats. Our results evidence that progesterone changes benzene toxicity (generation of ROS, oxidative stress). However, the probable antioxidative effect of progesterone needs to be confirmed by further studies.Benzen se u industriji često rabi kao otapalo. Zna se da na njegovu toksičnost mogu utjecati spolni hormoni, ali su mehanizmi njihova djelovanja još uvijek slabo poznati. Ispitali smo utjecaj progesterona na peroksidaciju lipida (malondialdehida), pad razina glutationa te aktivnost citokroma P450 2E1 (CYP2E1) u jetri i bubrezima štakorica. Primjena progesterona u štakorica koje su prethodno primile benzen inhibirala je stvaranje reaktivnih molekula kisika (engl. reactive oxygen species, krat. ROS), ali je u štakorica s ovariektomijom koje su također primile benzen doveo do značajnoga rasta glutationa u jetri. U štakorica koje su primile progesteron nije zamijećena poboljšana aktivnost izoeznima CYP2E1. Naši rezultati potvrđuju da progesteron utječe na toksičnost benzena (stvaranje ROS-a i oksidativni stres). Međutim, tek u budućim istraživanjima valja potvrditi djeluje li progesteron antioksidativno

Cytochrome P-450-Substrate Interaction and Hepatic Drug Metabolism in the Mouse

A drug which has entered the circulation, may be eliminated as such by the kidney and excreted in the urine. This depends on the lipid-solubility (lipophilicity) of the drug. In the kidney, lipid-soluble drugs are reabsorbed by the tubules, whereas water-soluble (hydrophilic) compounds cannot cross the tubular membrane. Upon passing through the liver some lipophilic drugs can be modified by conjugation with polar molecules, in order to be excreted in the bile or the urine, for example in the form of glucuronides. A large number of drugs, however, do not possess reactive groups for conjugation, They might tend to remain in the body, which is, in many cases, undesirable. In the liver, however, an enzyme system is present, which is capable of metabolizing these compounds by introducing polar groups with the aid of molecular oxygen, The metabolites produced may be excreted either directly or after subsequent conjugation

SEX-DEPENDENT DIFFERENCES IN DRUG METABOLISM IN THE RAT III. Temporal Changes in Type I Binding and NADPH-Cytochrome, P-450 Reductase during Sexual Maturation

ABSTRACT Microsomal ethylmorphine N-demethylase activity increased with age in male rats, but decreased with age in female rats. Relative to the cytochrome P-450 content of microsomes

The effects of some Chinese herbs on liver functions.

by Frankie Tat-kwong Lau.Bibliography: leaves 63-70Thesis (M.Ph.)--Chinese University of Hong Kong, 198

Role of Lipids in the Control of Sex Differences in the Phase I Metabolism of Drugs

Hepatic microsomal preparations from male and female rats were delipidated by column chromatography following cholate solubilisation. The enzyme activity was assayed using lignocaine as the substrate for the mixed function oxidase. The N-deethylation of lignocaine catalysed by delipidated microsomal proteins from male and female rat liver is greater when reconstituted in microsomal lipid than in dilauroylphosphatidylcholine (DLPC). The 3-hydroxylation of lignocaine is unaffected by this treatment. The above effect is mimicked by incorporation of dilauroylethanolamine (DLPE) into the DLPC vesicles with male- but not the female-derived enzymes. Microsomal lipids derived from the male were more effective than female-derived lipids in reconstituting enzyme activities with both male- and female-derived enzymes. There is, thus, a sex- and pathway dependent effect of the lipids: the male-specific N-deethylase pathway is more affected by lipid composition and then more so in the male-derived enzyme. It is possible, therefore, that some of the sex differences in drug metabolism may be related to changes in lipid composition. In addition, the sex-dependence of the metabolism of lignocaine was maintained in the reconstituted system, indicating that this is a suitable system for investigating the role of lipids in maintaining sex-specific drug metabolism. We have extended this work with the isolation of the isozyme of cytochrome P-450 responsible for the N-deethylation of lignocaine. The male-specific cytochrome P-450 isozyme, lignocaine N-deethylase, was purified to electrophoretic homogeneity from liver microsomes of untreated male rats with high retention of bioactivity. The purified N-deethylase was an efficient catalyst of the 16alpha-hydroxylation of androst-4 ene3,17-dione (specific activity of 10 nmole product/min/ nmole cytochrome P-450). The isozyme, together with purified NADPH-cytochrome P-450 reductase, was reconstituted using known lipids and the drug-metabolising activity assayed using lignocaine as substrate. The results showed that the purified isozyme only N-deethylated lignocaine and led to the following conclusion, (I) Mixed dilauroylphosphatidylcholine (DLPC)/dilauroylphosphatidylethanolamine (DLPE) vesicles gave a higher N-deethylase activity than DLPC vesicles. (II) The N-deethylation of lignocaine catalysed by a purified male-specific cytochrome P-450 from rat liver is greater when reconstituted in microsomal lipid than in DLPC. (III) Microsomal lipids derived from male were more effective than female-derived lipids in reconstituting enzyme activities. These data indicated that it is a direct interaction of the lipid with the enzyme (s) or an alteration of the protein-protein interactions caused by the lipid which leads to the change in enzyme activity and that it is the isozyme responsible for the N-deethylation that is particularly affected in this way. In order to assess which portion of the microsomal lipid causes these changes, the microsomal lipid has been fractionated into phospholipid and neutral lipid. Using delipidation and subsequent relipidation of microsomal lipid preparation, we have confirmed that the phospholipid is the most effective portion for the maintenance of the drug metabolism and the sex differences in drug metabolism. It is clear that the male-derived phospholipid was more efficient than the female-derived phospholipid when incorporated into both male- and female-derived delipidated microsomes. The mixture of phospholipid and neutral lipid fractions was very effective, indeed it restored the N-deethylase activity to the level of the microsomes. Experiments were carried out using the male-specific isozyme responsible for the N-deethylation of lignocaine and again it was shown that the phospholipid fraction was the most effective fraction when reconstituted with this isozyme, but it was less effective than the whole microsomal lipid. It is only when the combination of phospholipid and neutral lipid was used that the control activity was achieved. Again the male derived phospholipid was more effective than the female-derived phospholipid. We analysed the phospholipid composition and our analysis shows sex differences in microsomal phospholipid composition and in fatty acid acyl chain of the microsomal phospholipid. Also the analysis of the phospholipid from the diabetic animals showed that the streptozotocin treatment does alter the phospholipid composition and the ratio of acyl chains found. All these changes might be associated with differences in enzyme activity. (Abstract shortened by ProQuest.)

Evaluation of the anti-diabetic properties of Averrhoa bilimbi in animals with experimental diabetes mellitus

Ph.DDOCTOR OF PHILOSOPH