© 1993 Oxford University Press
research-article |
Subacute Toxicity of a Novel Inhibitor of Acyl-CoA: Cholesterol Acyltransferase in Beagle Dogs1
Departments of Pathology and Experimental Toxicology, Warner-Lambert Company 2800 Plymouth Road, Ann Arbor, Michigan 48105 *Department of Pharmacology, Parke-Davis Pharmaceutical Research Division, Warner-Lambert Company 2800 Plymouth Road, Ann Arbor, Michigan 48105
Received January 27, 1992; accepted October 16, 1992
PD 1323012 is a substituted urea hypolipidemic and antiatherosclerotic agent that is a potent inhibitor of acyl-CoA:cholesterol acyltransferase (ACAT). To determine its subacute toxicity, PD 1323012 was administered orally to beagle dogs at 0, 6, 12, 25, 50, 200, 400, or 800 mg/kg/day for 2 weeks. Clinicopathologic evaluations were completed on all dogs. Liver and adrenal total and esterified cholesterol concentrations, adrenocorticotrophic hormone (ACTH) responsiveness, and adrenal ultrastructure were determined at 0, 6, 12, and 25 mg/kg. At 12 mg/kg or greater, salivation, epiphora, conjunctivitis, emesis, anorexia or decreased food consumption, and soft to mucoid feces and/or diarrhea were noted. Suppression of ACTH response occurred by Day 6 at all doses. Adrenocortical degeneration and/or necrosis in zona fasciculata and reticularis was seen at all doses; adrenal free and esterified cholesterol were normal at 6 mg/kg and decreased at 12 and 25 mg/kg. Increases in serum alanine aminotransferase (2- to 15-fold), aspartate aminotransferase (2- to 12-fold), and alkaline phosphatase (2- to 7-fold) were noted at 50 mg/kg or greater. Periportal hepatocellular hypertrophy and hypereosinophilia occurred at 50 mg/kg or greater; hepatic cholesterol values were not significantly affected by treatment. Dose-dependent ultrastructural alterations in adrenocortical cells included decreased numbers of mitochondria and smooth endoplasmic reticulum profiles, qualitative and quantitative changes in lipid globules, and increased numbers of autolysosomes. PD 132301-2 or one of its metabolites has potent adrenocorticolytic properties and limited hepatotoxic properties by mechanism(s) that are likely independent of systemic ACAT inhibition.