Systems approach to study of solute transport across membranes using suspension cultures of mammalian cells IV: Uptake and release kinetics of sterols.
The kinetics of uptake and release of desmosterol, cholesterol, and beta-sitosterol by Burkitt lymphoma cells at 26 degrees, pH 7.3, and isoosmotic conditions were quantitatively and mechanistically interpreted. The data are in agreement with the model involving the passive transport of the unbound sterol across the rate-determining plasma membrane, with rapid distribution within the heterogeneous cell interior. Effective permeability (P-e) and partition (K-e) coefficients of the sterols were inversely proportional to the serum concentration in the external media due to sterol-serum binding. These results are consistent with the mechanism in which only the unbound solute in the external solution participates in the membrane transport process. At all serum levels, P-e and K-e increased with increasing sterol polarity: desmosterol greater than cholesterol greater than beta-sitosterol.
D000818:Animals; D002051:Burkitt Lymphoma; D002417:Cattle; D002463:Cell Membrane Permeability; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism*; D003897:Desmosterol / Q000378:metabolism*; D005333:Fetus; D007700:Kinetics; D008954:Models, Biological; D010539:Permeability; D012044:Regression Analysis; D012855:Sitosterols / Q000378:metabolism*
D012855:Sitosterols; D003897:Desmosterol; D002784:Cholesterol