title: Failure of filipin to detect cholesterol-rich domains in smooth muscle plasma membrane.
abstract: Using the cholesterol probe filipin and freeze-fracture electron microscopy, Montesano reported an apparent difference in cholesterol content between contiguous zones of the smooth muscle plasma membrane. In this membrane, microinvaginations termed caveolae are organized in band-like domains, which were highly sensitive to filipin (and therefore cholesterol-rich) compared with the surrounding non-caveolar inter-band regions (assumed to be cholesterol-poor). Using another cholesterol probe, the saponin tomatin, applied alone and after filipin treatment, we now present evidence that both the band and inter-band domains of the smooth muscle plasma membrane are cholesterol-rich. This leads to the conclusion that the lack of inter-band response to filipin is a false-negative cytochemical result.
mesh_terms: D000818:Animals; D001011:Aorta / Q000648:ultrastructure; D002462:Cell Membrane / Q000187:drug effects / Q000648:ultrastructure; D002784:Cholesterol / Q000032:analysis*; D005372:Filipin / Q000494:pharmacology; D005614:Freeze Fracturing; D008563:Membrane Lipids / Q000032:analysis*; D008854:Microscopy, Electron; D009131:Muscle, Smooth, Vascular / Q000648:ultrastructure*; D011817:Rabbits; D014053:Tomatine / Q000494:pharmacology
chemical_list: D008563:Membrane Lipids; D014053:Tomatine; D005372:Filipin; D002784:Cholesterol