Lipoproteins of human peripheral lymph.

The concentration of cholesterol in peripheral lymph is roughly one tenth of that in the blood plasma of the same subject. In lymph, there is virtually no very low density lipoprotein (VLDL), probably due to low permeability of the vascular endothelium for particles of this size. More than 95% of apo B-containing lipoproteins of lymph have the density of plasma low density lipoproteins (LDL). The concentration of apo A-I and apo A-II in lymph is about 15% of that in plasma; yet about 50% of the total mass of both these main HDL apoproteins is present extravascularly. High density lipoproteins (HDL) of lymph appear square-packing, and the presence of such large HDL particles is the most conspicuous difference between lipoproteins in plasma and in the extravascular fluids. It remains to be seen whether raising plasma apo A-I concentration per se will increase the initial stages of reverse cholesterol transport and also be clinically beneficial.