Isolated rat hepatocytes in suspension: potential hepatotoxic effects of six different drugs.

Isolated rat hepatocytes in suspension were studied with regard to various measures of hepatic toxicity. We compared enzyme leakage (ASAT, ALAT, LDH), cell viability (trypan blue exclusion), intracellular ATP content, and incorporation of 14C-valine into stationary and export proteins while the cells were exposed to six different drugs at two different concentrations. The drugs were oxytetracycline, paracetamol, carbon tetrachloride, ethanol, methotrexate and fentanyl. The results were compared to known in vivo responses, in particular to see whether concentrations resulting in dose-related in vivo effects would similarly affect the functions tested in vitro. Leakage of enzymes exhibited a graded increase with a corresponding rise in the concentration of oxytetracycline and carbon tetrachloride. Reduction in incorporation of 14C-valine into cell and medium proteins showed a similar graded effect with rising concentrations of paracetamol, carbon tetrachloride, and ethanol. Intracellular levels of ATP gradually decreased with increasing concentrations of carbon tetrachloride and ethanol. An obvious reduction in viability was only registered with increasing concentrations of carbon tetrachloride, while paracetamol tended to give a similar response. We found no major discrepancies between already known in vivo effects and our in vitro results when testing paracetamol, carbon tetrachloride, ethanol, methotrexate, and fentanyl. We could not, however, demonstrate inhibition of protein synthesis by oxytetracycline at the concentrations tested. No single measurement was adequate for testing all drugs. The test of 14C-valine incorporation into hepatocyte export proteins plus LDH leakage seemed to constitute a useful combination in detecting drug toxicity in hepatocyte suspensions.