title: The cholesterol content of the human erythrocyte influences calcium influx through the channel.
abstract: In order to study the influence of the cholesterol content on the calcium entry channel, the human red blood cell was used as a model system. The cholesterol to lecithin ratio (C/L ratio) of the membrane was modified experimentally by incubating the cells (15h, 25 degrees) with liposomes of defined C/L ratios. Subsequently, net 45Calcium-influx into the cell was measured by inhibiting the Ca-ejecting ATPase with vanadate. Additionally, the use of nitrendipine, a potent calcium channel inhibitor, during incubation allowed the determination of Ca-influx through the calcium channel. A positive correlation between the 45Ca++-influx and the molar C/L ratio of the membrane was found over a wide C/L range. A molar C/L ratio of 1.4 in the membrane increased calcium influx by 150 % compared to controls (molar C/L ratio = 0.8, calcium influx rate = 100 %), while a molar C/L ratio at less than 0.75 decreased calcium influx by 50 %. We conclude, that the cholesterol content of the membrane greatly influences the calcium channel and thus plays a pivotal role for the availability of calcium as a second messenger. These findings may provide a link between high plasma cholesterol and the development of atherosclerosis as well as enhanced platelet aggregability.
mesh_terms: D002118:Calcium / Q000097:blood*; D002784:Cholesterol / Q000097:blood*; D004912:Erythrocytes / Q000032:analysis*; D006801:Humans; D007473:Ion Channels / Q000378:metabolism*; D007700:Kinetics; D008081:Liposomes / Q000378:metabolism; D009543:Nifedipine / Q000031:analogs & derivatives / Q000494:pharmacology; D009568:Nitrendipine; D010713:Phosphatidylcholines / Q000097:blood; D013997:Time Factors
chemical_list: D007473:Ion Channels; D008081:Liposomes; D010713:Phosphatidylcholines; D002784:Cholesterol; D009568:Nitrendipine; D009543:Nifedipine; D002118:Calcium