In vitro characterization of two types of LDL apheresis module and effect of repetitive LDL apheresis on plasma cholesterol levels and aortic atherosclerosis in heterozygous WHHL rabbits.

In vitro filtration was used to characterize and compare the function of two types of LDL apheresis module: membrane filtration (module M: pore diameter, 0.04 micron; effective surface area, 0.1 m2) and LDL adsorption (module A: a column containing 20 ml of polyvinyl alcohol gels fixed with polyacrylic acid). Module A had better selectivity of LDL removal, while module M could rapidly remove a larger amount of LDL. The effect of repetitive LDL apheresis with module A on the plasma cholesterol level and on the development of aortic atherosclerosis was examined in 6 heterozygous WHHL rabbits (5 to 10 months old; mean plasma total cholesterol level, 270 +/- 39 mg/dl), treated with LDL apheresis at weekly intervals for 2 months. Plasma total and LDL cholesterols were lowered approximately 40% by a signal procedure. The LDL cholesterol level tended to decrease as treatment progressed, while the HDL cholesterol level was unchanged or rose above the baseline value in a week after LDL apheresis. The ratio of atherosclerotic lesion area to whole aortic area was relatively low in treated rabbits (6.5 +/- 1.9%) in comparison with that in 5 untreated heterozygous WHHL rabbits (18.3 +/- 7.7%). The mean cholesterol content in the thoracic aorta was 4.9 +/- 1.3 mg/g wet tissue in treated rabbits vs 13.3 +/- 6.1 mg/g wet tissue in untreated rabbits. These results suggest that repetitive LDL apheresis might be effective in maintaining a lower level of LDL cholesterol and retarding the atherosclerotic process in vivo.