Distribution of plasmalemmal vesicles on arterial endothelial surface as determined by freeze cleavage

The freeze-fracture technique was used to study the density and distribution of plasmalemmal vesicles at the endothelial surface of canine carotid arteries. The fractured surface of the endothelium can be divided into areas with vesicles (Aves) and areas without vesicles (Anves), the latter being located at the parajunctional zone. With morphometric analysis, Aves and Anves were found to be 75% and 25% of the endothelial surface, respectively. The average width of Anves (distance from the intercellular cleft) is approximately 0.4 micron. In Aves, the density of vesicles is 120 micron-2, and approximately 16% of Aves is covered by the vesicle orifices. The tight junctions appear as long and straight strands, 8-9 nm in width. The number of the strands varies from one to five. The gap junctions consist of closely packed particles 9-10 nm in size which form patches or plaques from 80 to 800 nm in size. These findings provide the quantitative information needed for the theoretical modeling of transendothelial vesicular transport of macromolecules.