LIPID COMPOSITION OF OPTIC NERVE MYELIN

Abstract— Myelin was isolated from bovine optic nerves by differential ultracentrifugation and its lipid composition was analysed. Optic nerve myelin contained 76·3 per cent lipid. The major lipids were cholesterol, ethanolamine glycerophosphatides (EGP) and cerebroside. Serine glycerophosphatides (SGP), sphingomyelin and cerebroside sulphate were present in smaller proportions. EGP and SGP contained 34·6 and 0·5 per cent aldehydes. The major fatty aldehydes were palmitaldehyde, stearaldehyde and octadecenaldehyde. The fatty acids of EGP, SGP and choline glycerophosphatides (CGP) were chiefly 16:0, 18:0 and 18:1, with small proportions of 20 and 22 carbon polyunsaturates. The sphingolipids contained predominantly saturated and monounsaturated fatty acids of chain lengths of 20–26 carbon atoms. Optic nerve myelin and white matter myelin resembled one another closely in overall lipid composition and in the fatty acid compositions of their constituent lipids. Optic nerve myelin and white matter myelin are chemically similar membranes, but both of these differ in their lipid composition from spinal root myelin.