Enhancement of acyl coenzyme A:retinol acyltransferase in rat liver and mammary tumor tissue by retinyl acetate and its competitive inhibition by N-(4-hydroxyphenyl) retinamide.

Retinol esterification by microsomal acyl coenzyme A:retinol acyltransferase was quantified in rat mammary tumor and liver tissue. Acyltransferase activity in the livers of mammary tumor-bearing rats was 40% of that in normal animals. In response to daily oral doses of 2 mg retinyl acetate for 18-19 days, activity increased 2.8-fold in transplanted rat mammary tumors, 4.1-fold in the livers of tumor-bearing rats, and 1.5-fold in the livers of normal rats. The in vitro esterification of retinol was competitively inhibited by all-trans-N-(4-hydroxyphenyl) retinamide (Ki = 154 microM).