Adenylate cyclase and a fatty acid spin probe detect changes in plasma membrane lipid phase separations induced by dietary manipulation of the cholesterol:phospholipid ratio.
Rats fed with a cholesterol supplement to their diet exhibited an increase in their plasma membrane cholesterol phospholipid (C/P)-lipid molar ratio from 0.72 to 0.98, whereas those fed the hypocholesterolaemic drug clofibrate in their diet exhibited a decrease in this ratio to 0.62. The properties of these membranes were analysed with regard to ligand-stimulated adenylate cyclase activity and the mobility of a fatty acid spin probe which allowed lipid phase separations to be identified. Membranes with elevated C/P ratios exhibited two distinct lipid phase separations, one at around 36 degrees C that was attributed to the external half of the bilayer and one at around 22 degrees C which was attributed to the inner half of the bilayer. Membranes with lowered C/P ratios exhibited a single lipid phase separation occurring at around 21 degrees C which was attributed to the lipids of the inner half of the bilayer. These results were compared with those obtained by manipulation of C/P ratios in vitro using liposome-cholesterol exchange techniques. Dietary manipulation of the C/P ratio of plasma membranes in vivo led to alterations in the fold stimulation of adenylate cyclase by various stimulatory ligands.
Needham
L
L
Finnegan
I
I
Houslay
M D
MD
D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D002784:Cholesterol / Q000378:metabolism*; D002791:Cholesterol, Dietary / Q000494:pharmacology*; D002994:Clofibrate / Q000494:pharmacology; D004578:Electron Spin Resonance Spectroscopy; D005459:Fluorides / Q000494:pharmacology; D005934:Glucagon / Q000494:pharmacology; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008560:Membrane Fluidity / Q000187:drug effects*; D008563:Membrane Lipids / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013113:Spin Labels
D002791:Cholesterol, Dietary; D008563:Membrane Lipids; D010743:Phospholipids; D013113:Spin Labels; D005934:Glucagon; D002784:Cholesterol; D000262:Adenylyl Cyclases; D002994:Clofibrate; D005459:Fluorides