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 parace tamol are often used but, in vivo, injury is not apparent until 12 h o r later. Many agents which protect in the short-term in vitro systems, such as fructose and glycerol which are effective, even in the late p hase, after paracetamol has initiated injury, do not provide any prote ction in vivo. We have extended the in vitro liver slice system to a m ore realistic 18 h. Secondly, we have initiated injury with paracetamo l in vivo, then followed the progression of injury in an in vitro syst em. Control liver slices incubated in a HEPES Ringer solution with ant ibiotics over 18 h show little sign of injury as demonstrated by leaka ge of lactate dehydrogenase (LDH) into the medium or loss of potassium . Liver slices exposed to 10 mM paracetamol for 2 h in vitro show exte nsive 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 sh ow little LDH leakage at 6 h in vitro but by 18 h injury is very appar ent. 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.