Effect of pressure and stirring on in vitro aortic transmural 125I-albumin transport.

The in vitro transport of 125I-albumin across the endothelial-injured canine aortic preparation was studied as a function of pressure (P) at various locations (z) along the vessel from stirred and quiescent reagents [serum (S) and a comparable albumin (A) reagent] to study mechanisms of vascular protein accumulation. Uptake (M, nmol X cm-2) was calculated from tissue radioactivity and strain-corrected vessel specimen surface area. Corresponding transmural concentration distributions [c(x)] were measured by quantitative microautoradiography. The results showed that 1) M and c(x) increased with P, decreased with z, and were lower from S than from A; 2) changes in M with stirring failed to demonstrate significant concentration gradients in the liquid at the vessel interface even with large uptake rates; 3) the c(x) contours were consistent with simple diffusion and convection in a homogeneous slab; 4) c(x) in the media near the intima increased with P above the assumed equilibrium concentration, suggesting interstitial solute rejection or edema formation with P; and 5) lower c(x) with S than A was consistent with a decreased reagent albumin activity, tissue binding, or tissue hydration.