Comparative study of the influence of sphingomyelin on the fluidity and packing properties of the erythrocyte membrane of different mammals

S.I. GIORGETTI; P.M.RODI; A.M. GENNARO

Congreso; 2° Congress of the Latinoamerican Federation of Biophysical Societies (LaFEBS) y “XXXVII Congress of the Brazilian Biophysical Society; 2012

Latinoamerican Federation of Biophysical Societies

Lipid composition plays a central role in the function of cell membranes and governs physical membrane properties as permeability and fluidity. Mammal erythrocytes, while differing in size or shape, have essentially the same membrane organization and protein composition. The main difference in their membrane lipid composition is the sphyngomyelin (SM) content, which varies drastically among the different species. SM is, together with cholesterol, relevant in determining lipid conformational order and packing. Preferential interactions between SM and cholesterol have been reported in model systems which could be relevant in determining detergent solubililty. In this context, we study the eryhtrocyte membrane of four mammal species: human, bovine, equine and rabbit. The degree of lipid order was determined by EPR spectroscopy with the aid of the liposoluble spin labels n-SASL (n=5, 12 or 16). The strength of lipid-lipid interactions in each of the membranes was tested by determining their detergent resistance and the amount of cholesterol extracted under the action of methyl beta cyclodextrin. The detergent resistance was characterized by measuring the amount of insoluble phosphorus after the incubation in increasing concentrations of Triton X-100 and determining from the curve the detergent resistance parameter. Our results show a clear positive correlation among membrane lipid order, detergent resistance, and SM content. Besides, the different amount of cholesterol extracted by methyl beta cyclodextrin in the different membranes suggest preferential interactions between SM and cholesterol.