The subcellular localization of lipid in myelin-free axonal preparations.

Bovine myelin-free axonal preparations were subjected to a series of washes designed to partition membranes from other cellular components initially present in these preparations. These washes were composed entirely of membranous structures, essentially free of neurofilament protein subunits, and contained high specific activity of acetylcholinesterase, an axolemma-specific enzyme. The distribution of acetylcholinesterase in the washes paralleled the distribution of lipid and the lipid composition of these washes closely resembled that of bovine axolemma-enriched fractions. In addition, acetylcholinesterase, lipid and galactocerebroside were histo- and immunohistochemically localized on similar structures in the starting material. Our results demonstrate that some of the lipid in myelin-free axonal preparations may be accounted for by axolemma.