THE EFFECT OF BLOOD PRESSURE ON THE PASSAGE OF LABELED PLASMA ALBUMIN INTO CANINE AORTIC WALL

Abstract

The effect of blood pressure on the passage of albumin labeled with radio-active iodine into aortic wall was studied in vivo and in vitro. Albumin enters the inner layer of the aortic wall of the normotensive dog with a gradient of rates. It enters fastest proximally and progressively less rapidly down the length of the aorta. Elevation of the blood pressure in vivo by section of the carotid sinus depressor nerves produces a marked increase in the rate of entrance of labeled albumin into the inner layer of ascending aorta, a small increase in the rate of entrance into that layer of upper descending thoracic aorta, and no increase in the rate of entrance into that layer in the more distal parts of the aorta. Thus, hypertension makes the gradient of rates steeper. An increase in nonpulsatile pressure exerted on plasma in the lumen of the aorta isolated in vitro also accelerates the passage of albumin into the inner layer of aortic wall. This excludes the pulsatile nature of blood pressure as a necessary factor in the acceleration of the passage of albumin into the aortic wall.