The use of pig hepatocytes for cytotoxicity studies of veterinary drugs: A comparative study with furazolidone and other nitrofurans.

The possible use of primary cultures of pig hepatocytes for cytotoxicity studies of veterinary drugs was investigated using some nitrofurans. The substances tested were furazolidone, furaltadone, nitrofurazone, nitrofurantoin (at concentrations of 15-500 mum) and nitrovin (5-50 mum); acetaminophen (1-10 mm) was used as a positive control. The leakage of lactate dehydrogenase (LDH) from the cells into the medium could be measured at high concentrations of nitrofurantoin, nitrovin, nitrofurazone and acetaminophen. After incubation of the cells with high concentrations of any of the drugs, intracellular LDH activities were lower than in controls. The incorporation of [(14)C]leucine into proteins, especially those excreted into the medium, was shown to be a more sensitive parameter of nitrofuran toxicity than LDH leakage, and was decreased by all of the drugs at most concentrations. Intracellular levels of oxidized glutathione were increased upon exposure to any of the nitrofurans. However, only incubation with 500 mum-nitrofurantoin decreased intracellular levels of reduced glutathione (GSH). In all other cases GSH levels were unchanged or even elevated upon exposure. The most sensitive parameter measured was the accumulation of pyruvate and lactate in the medium after treatment with any of the nitrofurans except nitrovin. Experiments with furazolidone showed that this effect did not disappear immediately after the end of exposure and also that the effect accumulated upon repeated treatment of the cells, especially at low doses. The results of the study clearly demonstrate that primary cultures of pig hepatocytes can be used for cytotoxicity studies of veterinary drugs.