title: Alteration of synaptosomal plasma membrane cholesterol content: membrane physical properties and cation transport proteins.
abstract: The level of nerve membrane cholesterol was altered by in vitro incubation of rat brain synaptosomal plasma membrane with liposomes having varying cholesterol contents. The normal plasma membrane cholesterol/phospholipid ratio of 0.3-0.4 (mol/mol) could be decreased by about one-half or increased more than 100%. Fluorescence polarization measurements were made using the probe 1,6-diphenyl-1,3,5-hexatriene. At temperatures below 35 percent C, lowering membrane cholesterol led to increased apparent microviscosity, while raising cholesterol content produced little change. However, at 45 percent C a continuous direct relationship existed between experimental membrane cholesterol/phospholipid ratio (ranging from 0.18 to 0.73) and apparent microviscosity. Under standard liposome-synaptosomal plasma membrane exchange conditions, 80% of the initial specific [(3)H]saxitoxin binding activity to the voltage-dependent sodium channel and at least 95% of the (Mg2+,K+)-p-nitrophenylphosphatase activity were preserved. Our results indicate that neither the characteristics of toxin binding nor the kinetics of this enzyme activity is dependent upon membrane cholesterol content.
mesh_terms: D009597:4-Nitrophenylphosphatase / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism* / Q000502:physiology; D005454:Fluorescence Polarization; D007473:Ion Channels / Q000378:metabolism; D008081:Liposomes / Q000378:metabolism; D008297:Male; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D012530:Saxitoxin / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D013574:Synaptosomes / Q000378:metabolism*
chemical_list: D007473:Ion Channels; D008081:Liposomes; D012530:Saxitoxin; D002784:Cholesterol; D012964:Sodium; D009597:4-Nitrophenylphosphatase; D011188:Potassium