Inhibition of galactosamine cytotoxicity in an in vivo/in vitro hepatocellular toxicity model.
A combined in vivo/in vitro model of galactosamine hepatotoxicity was employed to test whether previously reported cytoprotective actions of cystamine administration on galactosamine-induced hepatic injury in vivo could be attributed to a direct action of cystamine on toxicant-challenged hepatocytes. In this model, male Sprague-Dawley rats received a 400 mg/kg galactosamine challenge via intraperitoneal injection 1 hr prior to portal vein cannulation for hepatocyte isolation. Isolated cells are established in monolayer culture and galactosamine-induced cellular injury is then expressed over the ensuing 24-48 hr in culture. Consistent with the biochemical basis of galactosamine-induced hepatocellular injury in vivo, cytotoxicity could be prevented by in vitro uridine treatments within 3 hr of the in vivo galactosamine challenge, but not when added 12 hr later. Cystamine, in contrast, exhibited a cytoprotective effect even when added to cultures 12 hr after the in vivo toxicant challenge. Post-toxicant cytoprotection by cystamine in vitro was concentration dependent and did not produce an alteration of hepatocyte nonprotein sulfhydryl content. Post-toxicant cytoprotection by uridine and cystamine in this in vivo/in vitro model of toxicity were fully consistent with in vivo protection from galactosamine-induced necrosis by these agents. This model eliminates potential "extrahepatic" mechanisms for cystamine's hepatoprotective effect and demonstrates a direct cytoprotective action on galactosamine-challenged hepatocytes.
D000818:Animals; D003538:Cystamine / Q000494:pharmacology; D005688:Galactosamine / Q000037:antagonists & inhibitors / Q000633:toxicity*; D007527:Isoenzymes; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008099:Liver / Q000187:drug effects*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D014529:Uridine / Q000494:pharmacology
D007527:Isoenzymes; D005688:Galactosamine; D007770:L-Lactate Dehydrogenase; D003538:Cystamine; D014529:Uridine