Plasma membrane steroidogenic cholesterol: the relative importance of membrane internalization rate and cholesterol extraction rate of internalized membrane.
Most cholesterol destined to become steroid hormone passes through the plasma membrane. Using MA-10 Leydig tumor cells as a model system, we determined that plasma membrane cholesterol disappeared 2.5-fold faster in cAMP-stimulated cells. Stimulation of MA-10 cells increased internalization so that 1.4-fold more membrane cycled through the cell per unit time. Increased internalization accounted for 26% of the cholesterol actually lost from cycling membrane. The remaining 74% was accounted for by increasing the extraction of cholesterol from internalized membrane.
Freeman
D A
DA
Division of Endocrinology, Metabolism, Hypertension, University of Oklahoma Health Sciences Center and VAMC, Oklahoma City 73104, USA.
Romero
A
A
Choi
Y S
YS
D000818:Animals; D000924:Anticholesteremic Agents / Q000494:pharmacology; D001692:Biological Transport / Q000502:physiology; D003994:Bucladesine / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism*; D000242:Cyclic AMP / Q000494:pharmacology; D007984:Leydig Cell Tumor / Q000378:metabolism*; D008148:Lovastatin / Q000494:pharmacology; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D013256:Steroids / Q000096:biosynthesis*; D014407:Tumor Cells, Cultured
D000924:Anticholesteremic Agents; D008565:Membrane Proteins; D013256:Steroids; D003994:Bucladesine; D002784:Cholesterol; D008148:Lovastatin; D000242:Cyclic AMP