LUMINAL SURFACE CONCENTRATION OF LIPOPROTEIN (LDL) AND ITS EFFECT ON THE WALL UPTAKE OF CHOLESTEROL BY CANINE CAROTID ARTERIES

Purpose: The effect of near-wall blood flow velocity and plasma filtration velocity across the arterial wall on luminal surface concentration of low-density lipoproteins (LDL) and the uptake of tritium-cholesterol were investigated. Methods: A numeric analysis of LDL transport in steady flow, over the range of physiologically relevant flow rates, predicted a surface concentration of LDL of 4% to 16% greater than that in the bulk flow. The LDL surface concentration increased linearly with filtration velocity and inversely with wall shear rate. Results: These were validated experimentally in canine carotid arteries. When the transmural pressure was increased from 100 to 200 mm Hg, the filtration Velocity increased from 5.13 x 10(-6) cm/sec to 8.41 x 10(-6) cm/sec, whereas the normalized uptake rate of tritium-cholesterol increased from 3.58 x 10(-4) cm/hour to 7.36 x 10(-4) cm/hour. Conclusion: These results indicate that lipids accumulate at the luminal surface in areas where blood flow velocity and wall shear stress are low and where the permeability of the endothelial layer is enhanced. Moreover, the rate of lipid infiltration into the blood vessel walls is affected by the luminal surface concentration. These findings are consistent with chronic hypertension and elevated blood cholesterol concentrations being major risk factors for atherosclerosis.