Quantitative analysis of blood vessel permeability of squirrel monkeys.

A mathematical transport model was derived to analyze in vivo low-density lipoprotein (LDL) transport across the aorta, peripheral muscular arteries, and major veins of squirrel monkeys (primates that develop diet-induced atherosclerosis similar to humans). Parameters determining the relative magnitudes of intimal permeability and diffusion within the vascular wall were optimized by nonlinear regression methods. Transmural LDL concentrations demonstrating discrete spatial resolution along the endothelial surface were previously obtained after 30 min of tracer circulation using quantitative autoradiography. In this study, intimal mass transfer coefficient (k1) was determined in 87 vascular regions representing 280 transmural profiles. As a result of this analysis, the value of k1 was 1.7 +/- 0.4 x 10(-9) cm/s for arteries, 2.9 +/- 0.3 x 10(-9) cm/s for veins, and 60 +/- 120 x 10(-9) cm/s for enhanced LDL uptake regions, which was a significant increase (P less than 0.01). The effective diffusion coefficient was 6.2 +/- 3.7 x 10(-10) cm2/s for all vascular regions examined. As a result of this analysis, focal regions of enhanced LDL uptake were explained solely on the basis of intimal permeability.