Biochemical alterations in guinea pig adrenal cortex following administration of PD 132301-2, an inhibitor of acyl-CoA:cholesterol acyltransferase.

To assess whether previously reported ultrastructural alterations of adrenocortical mitochondria induced by the acyl-CoA:cholesterol acyltransferase (ACAT) inhibitor PD 132301-2 are accompanied by functional deficits in tissue energy stores, phosphorylated adenine nucleotide levels in guinea pig adrenal cortex were quantitated. Adrenals of male guinea pigs were obtained at 1, 2, 6, or 24 hours after oral administration of 100 mg/kg PD 132301-2 or 0.5% methylcellulose vehicle. In treated animals, ATP levels and ATP/ADP ratios were decreased approximately 50% with concurrent increases in AMP. Calculated energy charge was also decreased; these decreases were maximal by 6 hours. Cholesterol esterification in adrenal cortex was inhibited, resulting in progressive accumulation of free cholesterol up to 3-fold over control by 24 hours, consistent with the ACAT inhibitory activity of the drug. These data suggest that PD 132301-2 distributes to the adrenal cortex where early alterations of tissue bioenergetics occur in a time frame consistent with ultrastructural alterations of mitochondria.