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Title: The use of isolated hepatocytes to study the toxic effects of chemicals
Author: Gwynn, Jennie
ISNI:       0000 0001 3523 2037
Awarding Body: University of Surrey
Current Institution: University of Surrey
Date of Award: 1981
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Some characteristics of rat hepatocytes, isolated by a non-perfusion technique, have been examined in order to validate their use for the investigation of chemically induced toxicity. Untreated hepatocytes synthesized protein, RNA and GSH and metabolised exogenous substrates. GSH was depleted during isolation but active resynthesis was evident on incubation in complete culture medium. The levels of GSH, ATP and cyclic AMP were similar to those reported in the literature for hepatocytes isolated by perfusion. Hence the hepatocytes were shown to possess a number of in vivo characteristics. Although there was an inherent variability between individual preparations characterised by the variability in, and lack of correlation between, the rate of protein synthesis, cell yield and viability, the effect of a number of xenobiotics were investigated. Paracetamol induced a rapid fall in ATP, dose-dependent inhibition of protein, RNA synthesis, and the metabolism of 7-EC, depletion of GSH and covalent binding of drug related material to protein. Exposure of cultured hepatocytes to 40mM paracetamol for < 4 hrs produced reversible inhibition of protein synthesis, but cell death was the result of a longer exposure. Safrole and phenobarbitone also induced a rapid fall in ATP levels followed by dose-dependent inhibition of protein and RNA synthesis. This was, therefore, a common sequence of events in response to a toxic insult but was unlikely to be the direct cause of cell death. The activities of 7-EC O-deethylase, NADPH[2] diaphorase, SDH and G6PDH were all increased in cultures treated with 2mM phenobarbitone (a concentration which did not cause cell death). Paracetamol also caused increases in NADPH[2] diaphorase activity. The effects of these xenobiotics in hepatocytes were compared and discussed. It was concluded that the cause of cell death was not identified and that it was unlikely to be due to one factor alone but to a combination of factors dependent on the level and duration of toxic insult and a decreased ability of the cell to repair damage. With further refinements cultured hepatocytes should provide a useful model for the investigation of mechanisms of chemically induced toxicity.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Biochemistry