COCAINE-INDUCED LIVER-INJURY IN MICE ELICITS SPECIFIC CHANGES IN DNA-PLOIDY AND INDUCES PROGRAMMED DEATH OF HEPATOCYTES

Liver injury was induced by a single dose (60 mg/kg) of cocaine in mal e albino Swiss mice untreated or pretreated with phenobarbital (in dri nking water 1 gm/L), for 5 days before cocaine administration. One par ameter of liver injury, serum isocitrate dehydrogenase activity, showe d sharp increases at 24 hr of cocaine treatment; we also noted decreas ed hepatic levels of ATP, GSH, cytochrome P-450 and NADPH/NADP(+) rati o and increases in malondialdehyde concentration. Histopathological st udy of liver slices showed perivenous and periportal necrosis induced by cocaine in untreated mice and mice pretreated with phenobarbital, r espectively. A regenerative postnecrotic response, which peaked at 48 hr, was demonstrated by the appearance of mitotic cells. Mitotic index analysis showed that proliferative cells appear to be unevenly distri buted in the hepatic acinus and were mainly located in the vicinity of the damaged acinar region. Genomic DNA ploidy and the distribution of DNA in the phases of the cell cycle were studied in nuclei of isolate d hepatocytes. At 12 hr of cocaine administration, both in untreated a nd phenobarbital-pretreated mice, the following changes were observed: a sharp decrease in tetraploid (4N) cells (40% to 17% and 25% to 6%, respectively) and octoploid (8N) cells (5% to 2% and 2% to 1%, respect ively), together with the appearance of a hypodiploid population (13% and 31%, respectively). Hypodiploid population was characterized as ap optotic cells by detection of DNA fragmentation in agarose gel. These results suggest that a significant percentage of cell death induced by cocaine occurs by means of the apoptosis death program. Comparison of the initial values of DNA ploidy with those obtained at 7 days of coc aine administration showed remarkable increases in polyploid populatio ns (4N and 8N) and a decrease in diploid cells (2N), indicating that t he process of differentiation occurs when liver restores its functiona lity.