Application to drug-food interactions of living cells as in vitro model expressing cytochrome P450 activity: enzyme inhibition by lemon juice.

Classical inhibitors of human cytochrome P450 3A4 activity, such as ketoconazol and quercetin, are tested to prove the efficiency of a new metabolisation model using living entire cells. Grapefruit juice is a well-known potent inhibitor of cytochrome P450 3A4 activity. With regard to the clinical relevance of grapefruit juice-drug interactions, an investigation of other common juices is undertaken with this in vitro model.

Simple and rapid enzymatic assay of ornithine decarboxylase activity.

Since the induction of putrescine synthesis by ornithine decarboxylase (ODC) is observed in many pathological and physiological processes, a useful and simple method to assay this enzyme activity should be an interesting tool to quantify the biological importance of its induction. An enzymatic method to assay ODC is reported here. This method is based on the reaction between putrescine and soya diamine oxidase.

Stability parameter estimation at ambient temperature from studies at elevated temperatures.

The determination of specific kinetic constants k(i) in pH-profile studies is often undertaken at ambient temperature. However, when dealing with a drug substance that is stable at ambient temperature, the pH-profile study is conducted at a chosen elevated temperature and the kinetic parameters are given at this particular elevated temperature. But in stability studies we generally need kinetic constants at ambient or storage temperature for practical reasons (information and storage conditions of formulation).

Photodynamic DNA damage mediated by delta-aminolevulinic acid-induced porphyrins.

The mutagenic properties of UVA are thought to be predominantly radical-mediated, which supposes endogenous sensitizers. In order to investigate a possible role of porphyrins, their synthesis was induced in a murine leukemia P388D1 cell model by treatment with delta-aminolevulinic acid (delta-ala). Intra-cellular protoporphyrin IX reached a plateau after about 2 h, whereas soluble porphyrins, probably the photostable uro- and/or coproporphyrins, were excreted.

Chromatographic determination of 8-oxo-7,8-dihydro-2'-deoxyguanosine in cellular DNA: a validation study.

Although a series of biomarkers are widely used for the estimation of oxidative damage to biomolecules, validations of the analytical methods have seldom been presented. Formal validation, that is the study of the analytical performances of a method, is however recognized as the best safeguard against the generation and publication of data with low reliability. Classical validation parameters were investigated for the determination of an oxidative stress biomarker, 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dG) in cellular DNA, by high-performance liquid chromatography coupled to amperometric detection (HPLC-EC); this modified base is increasingly considered as a marker of oxidative damage to DNA, but many questions are still raised on the analytical methods in use.