Comparison of cholesterol transport in pulmonary, peritoneal, and blood-derived macrophages from normo- and hypercholesterolemic rabbits

Cholesterol flux in cholesterol ester-loaded macrophages in an in vitro perfusion system

Cholesterol ester-loaded J774 macrophages attached to microcarrier beads were perfused or incubated with lipoproteins in vitro. Cholesterol influx was reduced by decreasing LDL cholesterol, efflux was promoted by increasing HDL cholesterol or by adding apolipoprotein A-I/phosphatidylcholine complexes to the perfusate or incubation medium. Addition of sera obtained from patients after LDL apheresis or plasma exchange resulted in much smaller increments in cell cholesterol than pretreatment sera, due to decreased influx, but efflux was unchanged despite the reduction in HDL cholesterol by plasma exchange. These data suggest that extracorporeal cholesterol removal promotes mobilization of intracellular cholesterol ester mainly by reducing cholesterol influx.

Impaired corticosteroid production by isolated adrenocortical cells of hypercholesterolemic rabbits

Changes in the structure and function of rabbit adrenocortical cells were studied eight weeks after cessation of a cholesterol-enriched diet. The plasma cholesterol level of the treated animals was still modestly elevated. All three zones of the adrenal cortex contained a slightly increased number of intracellular lipid droplets, and greater number of lipid-laden macrophages were located in the inner layers, as revealed by light and electron microscopy. The basal and ACTH-stimulated hormone production by the isolated adrenocortical cells were significantly inhibited compared with those of the controls. A possible causal relationship between the inhibited adrenocortical hormone production and the increased number of macrophages is discussed.