CHARACTERIZATION OF SUBPOPULATIONS OF LIPOPROTEIN PARTICLES ISOLATED FROM HUMAN CEREBROSPINAL-FLUID

The aim of the present study was to define lipoprotein complexes withi n cerebrospinal fluid (CSF) in terms of their apolipoprotein compositi on, using fractionation procedures considered optimal for maintaining lipoprotein structural integrity. Five apolipoproteins were identified , namely apolipoproteins A-I, A-IV, D, E and J. These were differentia lly distributed amongst lipoprotein particles of which three major sub populations were identified. CSF-LpAI (20.1 +/- 3.8 nm) was enriched i n apolipoprotein A-I and contained the major proportion (> 50%) of apo lipoproteins D, E and J. CSF-LpE, of similar size to CSF-LpAI (20.2 +/ - 3.1 nm), was composed principally of apolipoprotein E, with minor qu antities of apolipoproteins A-I, A-IV, D and J. Elimination of these p articles from cerebrospinal fluid by immunoabsorption revealed a third subpopulation of significantly greater diameter (32.0 +/- 6.8 nm). Th e majority (62%) of apolipoprotein A-IV was also present in this fract ion. The study demonstrates the structural and size heterogeneity of l ipoproteins in cerebrospinal fluid. This may reflect the lipid transpo rt processes within the central nervous system.