Studies on cholesterol accumulation in radicular cyst fluid--origin of heat-stable cholesterol-binding protein.

1. The amount of apolipoprotein B (apo B) was measured using slit-immunoblotting in 20 specimens of radicular cyst fluids. Apo B was detected in all the cyst fluids with varying amounts. 2. Relationship between the amounts of apo B and free cholesterol or activity of heat-stable cholesterol-binding protein (HCBP) were examined. The amount of apo B was correlated well with the activity of HCBP (n = 20, r = 0.72, P less than 0.01) and with the amount of free cholesterol (n = 20, r = 0.45, P less than 0.05). 3. Anti-human apo B antibody inhibited cholesterol-binding activity in radicular cyst fluid. 4. When human-serum was chromatographed on a HPLC ion-exchange column, both cholesterol-binding activity and apo B had exactly the same retention time. 5. These results suggest that HCBP originates from beta-lipoprotein, and beta-lipoprotein may have an important role in cholesterol accumulation on radicular cysts.