Journal of Lipid Research, Vol 26, 915-923, Copyright © 1985 by Lipid Research, Inc.
Comparison of cholesterol transport in pulmonary, peritoneal, and blood- derived macrophages from normo- and hypercholesterolemic rabbits
RN Fontaine and CJ Fielding
The influx and efflux components of cholesterol transport were separately
determined in pulmonary, peritoneal, and monocyte-derived macrophages from
rabbits fed a diet containing either 4.5% fat or 4.5% fat plus 2%
cholesterol. Both influx and efflux in pulmonary macrophages increased with
increasing concentration of either normal or hypercholesterolemic serum in
the medium. The mass of cholesterol entering the macrophages continued to
increase beyond the mass of cholesterol effluxed, leading to an increase in
cholesterol mass. Similar results were obtained with peritoneal
macrophages. Cholesterol- enriched peritoneal macrophages in most cases had
a net efflux of sterol when incubated with normocholesterolemic serum.
Pulmonary and peritoneal macrophages from cholesterol-fed rabbits tended to
have slower sterol influx and a slightly faster sterol efflux than
pulmonary and peritoneal macrophages from control rabbits, but the combined
effect of these mechanisms did not prevent these macrophages from
accumulating sterol ester from hypercholesterolemic serum.
Hypercholesterolemic rabbit serum was fractionated by heparin-Sepharose
affinity chromatography into a beta-VLDL-deficient nonadsorbed fraction,
which had very little effect on pulmonary macrophage sterol content, and an
adsorbed beta-VLDL-containing fraction which promoted a large increase in
macrophage sterol. As with unfractionated hypercholesterolemic serum,
macrophages incubated with the adsorbed beta-VLDL-containing fraction
accumulated large amounts of cellular sterol. Monocyte-macrophages cultured
in vitro for 21 hr, in contrast to extravascular macrophages, closely
regulated their cellular sterol, primarily by limiting the rate of sterol
influx.