APOLIPOPROTEINS IN RAT CEREBROSPINAL-FLUID - A COMPARISON WITH PLASMA-LIPOPROTEIN METABOLISM AND EFFECT OF AGING

Cerebrospinal fluid (CSF) apo E concentrations, determined by a sensitive sandwich ELISA, were 411.3 +/- 76.0 and 454.3 +/- 51.8-mu-g/dl (mean +/- S.D.) for young rats (8-12 weeks old, n = 7) and old rats (36-40 weeks old, n = 10), respectively. Age-related increase, which was conspicuous in serum apo E (21.2 +/- 2.4 vs 60.9 +/- 14.1 mg/dl for young and old rats, respectively), was not observed in CSF apo E. CSF apo A-I concentrations, determined by ELISA, were extremely low in the both groups (< 10-mu-g/dl). Neither CSF apo A-I nor CSF apo E correlated to any of the plasma lipoprotein components, indicating the presence of largely independent lipoprotein metabolism in the rat central nervous system. Apo E is present in CSF in the form of apo E-rich HDL1 with particle sizes similar to those of plasma E-rich HDL1.