Arterial permeability to labeled protein.

Labeled albumin, which was administered intravenously, was detected, with the use of a scintillation counter, in the aortic wall of rabbits. Relative to weight, the permeability index was highest in the aortic arch and abdominal aorta and lowest in the medial thoracic aorta. Angiotensin II and various mediators were found to increase the permeability of the aortic wall.