COCAINE TOXICITY IN CULTURED CHICKEN HEPATOCYTES - ROLE OF CYTOCHROME-P450

Cocaine (COC) causes liver damage in several species, including man. C hicken embryo hepatocyte cultures were evaluated as a model system to investigate the mechanism of cocaine-mediated hepatotoxicity. Paramete rs used to assess toxicity were: (1) release of lactate dehydrogenase (LDH); (2) decreased induction of 5-aminolevulinic acid synthase (ALAS ), measured as porphyrin accumulation; and (3) decreased protein synth esis. Exposure of untreated cultures to COC or norcocaine (NOR) caused dose-dependent increases in LDH release, decreased protein synthesis, and eventual cell death. Pretreatment with 2-propyl-2-isopropylacetam ide (PIA), a phenobarbital-like inducer of cytochrome P450, accelerate d toxicity and lowered the threshold dose at which toxicity occurred. PIA pretreatment also increased rates of elimination of both COC and N OR and increased rates of formation of NOR from COC. The toxicity of C OC and NOR could also be detected as decreased porphyrin accumulation. Addition of the P450 inhibitor SKF-525A concurrently with COC or NOR decreased their rates of elimination. SKF-525A also prevented the incr ease in LDH release as well as the decrease in protein synthesis cause d by treatment with COC or N-hydroxynorcocaine (N-OH). Addition of SKF -525A up to 3 hr after COC resulted in partial prevention of the LDH i ncrease. Exposure of the cultures to COC induced cytochrome P450 2H pr otein. We conclude that this hepatocyte culture system is highly sensi tive to COC toxicity and that constitutive as well as induced cytochro me P450 isoforms are involved in the production of liver damage from C OC. (C) 1994 Academic Press, Inc.