Cell injury and protection in long-term incubation of liver slices after in vivo initiation with paracetamol: Cell injury after in vivo initiation with paracetamol

Short-term in vitro methods (2-6 h) for study of cell injury by paracetamol are often used but, in vivo, injury is not apparent until 12 h or later. Many agents which protect in the short-term in vitro systems, such as fructose and glycerol which are effective, even in the late phase, after paracetamol has initiated injury, do not provide any protection in vivo. We have extended the in vitro liver slice system to a more realistic 18 h. Secondly, we have initiated injury with paracetamol in vivo, then followed the progression of injury in an in vitro system. Control liver slices incubated in a HEPES Ringer solution with antibiotics over 18 h show little sign of injury as demonstrated by leakage of lactate dehydrogenase (LDH) into the medium or loss of potassium. Liver slices exposed to 10 mM paracetamol for 2 h in vitro show extensive LDH leak at 6 h which is even more severe at 18 h. Liver slices from animals treated with paracetamol (1 g/kg i.p.) in vivo for 3 h show little LDH leakage at 6 h in vitro but by 18 h injury is very apparent. Fructose and glycerol which protect against paracetamol injury in the short-term (6-h) in vitro system, do not do so when observations are extended to 18 h. They also fail to provide any protection to the slice from animals pre-treated in vivo with paracetamol. Other agents show similar affects. There is no convincing evidence that these short-term protective agents afford any protection in vivo and we show that ibuprofen and dexamethasone do not protect in vivo. It is clear that short-term assays for cell protection have only a limited explanatory value.