The permeability of large arteries to labeled protein.

Using labeled albumin, the permeability index was determined for the aorta and other arteries of the rabbit after different circulation times. The results were reproducible. Different indices of permeability were obtained for different arteries. When the circulation time of the tracer was extended, the increase in the permeability index was greater for the coronary and femoral arteries than for the aorta. 5-hydroxytryptamine, bradykinin and prostaglandin E2 tended to increase the permeability index. There was no relation to the level of blood pressure. The different indices of permeability obtained for the different arteries were not leveled by the mediators. The permeability index is seen to become greater postmortally.