Structural requirements of sterols for myelin tube formation with sodium oleate.

Cholesterol crystals treated with an aqueous solution of sodium oleate give rise to cylindrical lamellar associations which appear under the microscope as rapidly growing tubes. Myelin forms are also obtained with other membrane sterols (desmosterol, cholestanol, 7-dehydrocholesterol) but not with lanosterol, a metabolic precursor of cholesterol, nor with the catabolic products of cholesterol (coprosterol, cholecalciferol, pregnenolone). The structural requirements for obtaining myelin tubes from sterols and sodium oleate closely agree with the results obtained by studying sterol-lecithin associations using other experimental techniques (unimolecular films at the air/water interface and permeability of liposomes), association of sterols with an erythrocyte protein and cholesterol liquid crystals.