title: Factors determining detergent resistance of erythrocyte membranes.
abstract: The degree of detergent insolubility of cell membranes is a useful parameter to test the strength of lipid-lipid interactions relative to lipid-detergent interactions. Thus, solubility studies could give insights about lipid-lipid interactions relevant in domain formation. In this work we perform a detailed study of the solubilization of four different erythrocyte membrane systems: intact human and bovine erythrocytes, and human and bovine erythrocytes depleted in cholesterol with methyl-beta-cyclodextrin. Each system was incubated with different concentrations of the non-ionic detergent Triton X-100, and the insoluble fraction was characterized by determining cholesterol and phosphorus content. A distinct solubilization behavior was obtained for the four systems, which was quantified by a "detergent resistance parameter" obtained from the fit of the solubility curves. In order to correlate these findings with membrane structural parameters, we quantify the degree of acyl chain order/rigidity of the original membranes by EPR spectroscopy, finding that detergent resistance is higher when acyl chains are more rigid. Regarding compositional properties, we found a good correlation between detergent resistance parameters and the total amount of cholesterol plus sphingomyelin in the original membranes. Our results suggest that a high degree of acyl chain packing is the determinant membrane factor for resistance to the action of Triton X-100 in erythrocytes.
authors.affiliation: Departamento de Física, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral (UNL), Ciudad Universitaria, 3000 Santa Fe, Argentina.
authors.forename: P M
authors.initials: PM
authors.lastname: Rodi
authors.forename: V M
authors.initials: VM
authors.lastname: Trucco
authors.forename: A M
authors.initials: AM
authors.lastname: Gennaro
mesh_terms: D000818:Animals; D002417:Cattle; D002784:Cholesterol / Q000032:analysis / Q000737:chemistry; D003902:Detergents / Q000737:chemistry*; D004910:Erythrocyte Membrane / Q000737:chemistry*; D006801:Humans; D017830:Octoxynol / Q000737:chemistry; D010539:Permeability; D012995:Solubility; D047392:beta-Cyclodextrins / Q000032:analysis
chemical_list: D003902:Detergents; D047392:beta-Cyclodextrins; D017830:Octoxynol; D002784:Cholesterol