THE PERMEABILITY OF THE CAPILLARY WALL TO THE DIFFERENT PLASMA LIPOPROTEINS OF THE HYPERCHOLESTEROLÆMIC RABBIT IN RELATION TO THEIR SIZE

¹ Department of Experimental Pathology, John Curtin School of Medical Research, Australian National University, Canberra

The lipoproteins in the plasma of the cholesterol-fed rabbit were separated in the Spinco model L preparative ultracentrifuge into three fractions at densities of 1·019, 1·063 and 1·200.

The size of these three lipoprotein fractions was determined by measuring the lymph : plasma ratios of the respective concentrations both before and after injuring the leg by a thermal burn. The mean ratios for the three fractions were 7·1, 20·3 and 36·6 before injury and 39·4, 53·0 and 70·1 after injury, indicating that in both cases the degree of transference of each fraction was roughly proportional to the size of the macromolecules.

When Lipomul, an artificial fat emulsion with larger lipid particles which do not pass through the capillaries of the leg, was infused intravenously into a hypercholesterolæmic rabbit, the lymph : plasma lipid ratio greatly decreased. This was interpreted as due to the uptake of some of the smaller lipoproteins by the larger Lipomul particles, so reducing the degree of transference across the capillary wall. The possible mechanisms for the transference of the lipoproteins from plasma to lymph, involving the walls of both the blood and lymphatic capillaries are discussed.

Note:

We wish to acknowledge the contribution of the electron-microscopist, Mr. M. Taylor, in obtaining the electronmicrographs of the lipoproteins.