Cytosolic modulators of acyl-CoA: cholesterol acyltransferase (ACAT) activity in hepatic tissue of the chicken (Gallus domesticus).

1. An enzymatic assay for microsomal acyl-CoA: cholesterol acyltransferase (ACAT) activity in chicken hepatic tissues was developed using silicic acid chromatography. 2. ACAT activity was increased in response to liver cytosolic protein preparations suggesting the presence of cytosolic modulators of the enzyme. 3. Fractions containing low molecular weight proteins (12-15 kDa) prepared by molecular sieve chromatography also stimulated ACAT activity. 4. Liver-FABP was specifically implicated as a cytosolic modulator of ACAT activity in chicken liver tissue.