Acid Cholesterol Esterase Activity in the Foam Cells Isolated from Rabbit Experimental Xanthoma Tissues

Abstract

Acid cholesterol esterase (ACE) activity was assayed in the 10,000×g pellet from infiltrating cells isolated from experimental rabbit xanthoma tissues. Skin specimens were obtained from sites of intradermal dextran sulfate injections on a normolipemic rabbit (NLR) and a diet‐induced hypercholesterolemic rabbit (HCR). Most infiltrating cells were histiocytes or foam cells. Histiocytes from the NLR did not accumulate cholesteryl esters after the injections. Accumulation of cholesteryl esters in the xanthoma tissues of the HCR increased after repeating the injections at the same site. The ACE activity was greater in the cholesteryl ester‐accumulated foam cells than in histiocytes. The enzyme activity in the foam cells decreased during the developmental course of cholesteryl ester accumulation. These findings indicate that lysosomal ACE is activated and hydrolyzes the internalized cholesteryl esters of serum lipoprotein origin in the histiocytes which are transforming into foam cells. However, the enzyme activity decreases when too much of the cholesteryl esters has accumulated in the foam cells.