Journal of Lipid Research, Vol 26, 1285-1293, Copyright © 1985 by Lipid Research, Inc.
Influence of lecithin acyl chain composition on the kinetics of exchange between chylomicrons and high density lipoproteins
GM Patton, SJ Robins, JM Fasulo and SB Clark
The kinetics of lecithin exchange between native lipoproteins was
characterized for individual molecular species of lecithins of rat
mesenteric lymph chylomicrons and rat plasma HDL. Studies were performed in
the absence of lipid transfer proteins. Donor (chylomicrons) and acceptor
(HDL) particles were present in ratios of 1:1 and 1:10 with respect to
total phospholipid. Biphasic exchange kinetics were observed for all major
lecithins common to chylomicrons and HDL at both proportions of donor to
acceptor particles. During the early rapid phase of exchange, complete in
about 30 min, 40-60% of the total lecithin pool was exchanged. Initial
exchange rates were most rapid for the more hydrophilic species of the
major lecithins normally present in both lipoproteins. Calculated
activation energies correspondingly were least for a diunsaturated lecithin
(18:1-20:4), intermediate for lecithins were 16:0 in position-1 (16:0-18:2
and 16:0- 20:4), and highest for analogous lecithins with 18:0 in
position-1. A 10-fold increase in the ratio of acceptor to donor particles
affected neither the biphasic nature of the exchange nor the rates of
exchange of individual molecular species (consistent with exchange by
diffusion rather than by particle collisions). Total equilibration of
individual molecular lecithin species was achieved by 24 hr (37 degrees C,
donor to acceptor ratio of 1:1) with only a small change in the relative
mass of lecithins in chylomicrons and HDL. Novel lecithins containing 18:3,
incorporated into chylomicrons, were found to exchange exceedingly
rapidly.(ABSTRACT TRUNCATED AT 250 WORDS)
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