The Role of Beta-Lipoprotein,Cholesterol,and Various Sera in Tissue Culture Intracellular Lipidosis

Summary

Serum from human, calf, fetal calf, horse, and roosters fed either a regular or high cholesterol diet produced sundanophilic cytoplasmic inclusions within cloned mouse fibroblasts (“Low line” NCTC No. 2445) in tissue culture. Serum from roosters either fed a 1.0% cholesterol diet or subjected to heat stress exhibited an increased ability to produce cytoplasmic inclusion. The serum protein factor responsible for these inclusions proved to be the low density, β-lipoprotein. α-Lipoprotein produced inclusions only in high concentrations. Besides varying with different sera, the amount of lipidosis was found to be directly proportional to total cholesterol and to the percentage of β-lipo-protein-bound unesterified cholesterol, but inversely proportional to the percentage of bound esterified cholesterol. Furthermore, bovine albumin-bound cholesterol, only in the unesterified form, produced similar appearing sudanophilic, cytoplasmic inclusions. These observations suggest that the protein-bound, and more specifically, the β-lipoprotein-bound, unesterified cholesterol plays a significant role in inclusion formation, although other factors are porbably involved in this process.