Subcellular localization and quantification of cholesterol in cultured human fibroblasts exposed to human low density lipoprotein.

Subcellular localization of nonesterified cholesterol has been determined in normal human fibroblasts from cultures incubated with human low density lipoprotein (LDL). Nonesterified and esterified cholesterol content of fibroblasts, grown initially in the absence of cholesterol, increased significantly after a 1-hour incubation with LDL. Digitonin was used to localize nonesterified cholesterol that was accumulated within multivesicular and lamellar lysosomal inclusions. This was observed only in fibroblasts from cultures incubated with LDL. Accumulation of LDL-derived nonesterified cholesterol within lysosomes is consistent with the suggestion of other investigators that LDL is metabolized within lysosomes.