TETRACYCLINE-INDUCED STEATOSIS IN PRIMARY CANINE HEPATOCYTE CULTURES

Primary hepatocyte cultures prepared from male beagle dog liver were u sed to determine susceptibility of the canine liver to tetracycline-in duced steatosis. The effects of the drug on mitochondrial lipid metabo lism and intracellular triglyceride accumulation were monitored at the same time that steatosis was detected by light microscopy and quantit ated using lipid-specific stains. Exposure of primary canine hepatocyt e cultures to tetracycline for 24-48 h resulted in concentration-depen dent, significant increases in the Oil Red O-stained lipid inclusions. Microscopic examination of the total stained areas suggested that inc reases over control levels were due primarily to the increase in the s ize of the lipid inclusions rather than in the number. Biochemical ana lyses for triglyceride content and histological staining with Nile red , another neutral lipid-specific dye, confirmed a specific increase in intracellular triglyceride following a 24-h exposure to noncytotoxic levels of tetracycline. beta-oxidation studies based on the oxidation of [C-14]palmitic acid or [C-14]palmitoyl carnitine demonstrated a con centration-dependent inhibition of mitochondrial but not peroxisomal b eta-oxidation in hepatocytes after a 24-h exposure to tetracycline. In vitro incubation of tetracycline with mitochondria isolated from dog liver showed similar, concentration-dependent inhibition. This study c learly indicates that the canine hepatocyte is susceptible to tetracyc line-induced steatosis. Triglyceride accumulation was concomitant with the inhibition of mitochondrial lipid metabolism, indicating that thi s is a primary mechanism leading to steatosis in dog hepatocytes follo wing tetracycline exposure. (C) 1997 Society of Toxicology.