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 filtra tion velocity across the arterial wall on luminal surface concentratio n of low-density lipoproteins (LDL) and the uptake of tritium-choleste rol were investigated. Methods: A numeric analysis of LDL transport in steady flow, over the range of physiologically relevant flow rates, p redicted a surface concentration of LDL of 4% to 16% greater than that in the bulk flow. The LDL surface concentration increased linearly wi th filtration velocity and inversely with wall shear rate. Results: Th ese were validated experimentally in canine carotid arteries. When the transmural pressure was increased from 100 to 200 mm Hg, the filtrati on Velocity increased from 5.13 x 10(-6) cm/sec to 8.41 x 10(-6) cm/se c, 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: Thes e results indicate that lipids accumulate at the luminal surface in ar eas where blood flow velocity and wall shear stress are low and where the permeability of the endothelial layer is enhanced. Moreover, the r ate of lipid infiltration into the blood vessel walls is affected by t he luminal surface concentration. These findings are consistent with c hronic hypertension and elevated blood cholesterol concentrations bein g major risk factors for atherosclerosis.