Extravascular protein measurements in vivo and in situ by ultramicrospectrophotometry

Abstract

By means of ultramicrospectrophotometry the amount of extravascular plasma protein in the perivasal connective tissue was determined in vivo and in situ, using as an object the mesenterial plate of an everted intestinal loop of the rat. As with the circulating blood plasma, the protein content in the perivascular space lies in the range of 7–52%. We calculated the mean protein amount in 1 g of interstitial tissue as 3.4 mg. Outside the wall of venules the protein content was significantly higher than around capillaries or arterioles. Further from the vascular wall, the protein content decreases in the interstitial tissue. These concentration gradients were significantly higher around the venules than around the arterioles. The extravascular protein in steady state conditions of permeability is, therefore, not equally distributed within the interstitial space.