Measurement of malondialdehyde in cultures of adult rat hepatocytes

The Use of Long-term Hepatocyte Cultures for Detecting Induction of Drug Metabolising Enzymes: The Current Status

In this report, metabolically competent in vitro systems have been reviewed, in the context of drug metabolising enzyme induction. Based on the experience of the scientists involved, a thorough survey of the literature on metabolically competent long-term culture models was performed. Following this, a prevalidation proposal for the use of the collagen gel sandwich hepatocyte culture system for drug metabolising enzyme induction was designed, focusing on the induction of the cytochrome P450 enzymes as the principal enzymes of interest. The ultimate goal of this prevalidation proposal is to provide industry and academia with a metabolically competent in vitro alternative for long-term studies. In an initial phase, the prevalidation study will be limited to the investigation of induction. However, proposals for other long-term applications of these systems should be forwarded to the European Centre for the Validation of Alternative Methods for consideration. The prevalidation proposal deals with several issues, including: a) species; b) practical prevalidation methodology; c) enzyme inducers; and d) advantages of working with independent expert laboratories. Since it is preferable to include other alternative tests for drug metabolising enzyme induction, when such tests arise, it is recommended that they meet the same level of development as for the collagen gel sandwich long-term hepatocyte system. Those tests which do so should begin the prevalidation and validation process.

Mechanism of the protective action of taurine in toxin and drug induced organ pathophysiology and diabetic complications: a review

Taurine (2-aminoethanesulfonic acid), a conditionally essential amino acid, is found in large concentrations in all mammalian tissues and is particularly abundant in aquatic foods. Taurine exhibits membrane stabilizing, osmoregulatory and cytoprotective effects, antioxidative properties, regulates intracellular Ca(2+) concentration, modulates ion movement and neurotransmitters, reduce the levels of pro-inflammatory cytokines in various organs and controls blood pressure. Recently, emerging evidence from the literature shows the effectiveness of taurine as a protective agent against several environmental toxins and drug-induced multiple organ injuries as the outcome of hepatotoxicity, nephrotoxicity, neurotoxicity, testicular toxicity and cardiotoxicity in several animal models. Besides, taurine is also effective in combating diabetes and its associated complications, including cardiomyopathy, nephropathy, neuropathy, retinopathy and atherosclerosis. These beneficial effects appear to be due to the multiple actions of taurine on cellular functions. This review summarizes the mechanism of the prophylactic role of taurine against several environmental toxins and drug-induced organ pathophysiology and diabetes.

Antioxidant and hepatoprotective effects of artichoke extracts and constituents in cultured rat hepatocytes

Primary cultures of rat hepatocytes exposed to tert-butyl hydroperoxide (t-BHP) were used for characterizing the antioxidative and hepatoprotective potential of aqueous artichoke extracts (AK.) and some selected constituents. Addition of t-BHP to the culture medium resulted in enhanced lipid peroxidation measured as production of malondialdehyde (MDA) and enhanced cytotoxicity detected by LDH leakage. Aqueous artichoke extracts added prior or simultaneously with t-BHP reduced both phenomena with EC(50) values of about 95 and 12 mug artichoke powder/ml, respectively. Furthermore, AE prevented the loss of intracellular GSH caused by t-BHP. Several polyphenolic and flavonoid constituents of AE were found to reduce MDA production. EC(50) values were 8.1, 12.5, 15.2, 28 mug/ml for caffeic acid, chlorogenic acid, cynarin and cynarosid, respectively. A similar ranking for AE and constituents was found when using the chemiluminescent xanthine oxidase assay for determination of the antioxidative potency, but EC(50) values were consistently lower. Concerning the hepatoprotective effect, that is prevention of LDH leakage, all constituents were almost equipotent and EC(50) values were lower than for MDA production. These results suggest (i) that lipid peroxidation is not the primary cause for cytotoxicity of t-BHP, (ii) that hepatocyte cultures exposed to t-BHP represent a suitable model system for screening plant extracts for antioxidant and hepatoprotective effects, and (iii) that AE have a marked antioxidative and hepatoprotective potential which can be ascribed, at least partially, to some ubiquitous and artichoke-specific polyphenolic and flavonoid compounds.