The effect of bovine albumin on the permeability of frog mesenteric capillaries.

Abstract

Two types of experiment have been carried out to investigate the effect of albumin upon the permeability of frog mesenteric capillaries to unbound molecules of T1824. In the first series of experiments a single capillary was perfused, via a micropipette, with a Ringer solution containing T1824‐albumin complex and an excess of unbound T1824. The same capillary was then perfused with a solution containing approximately the same free T1824 concentration but no albumin. Experiments were carried out on fourteen capillaries and it was found that the presence of albumin approximately doubled the time of first appearance of dye outside the capillaries. In a second series of experiments a capillary was perfused with a solution of T1824 and no albumin, and the time of first appearance of dye outside the capillary was measured densitometrically. The same capillary was then perfused a second time with a solution containing approximately the same free dye concentration in the presence of T1824‐albumin complex. As soon as the capillary had filled with dye, it was closed off at a point downstream from the site of cannulation and the pressure in the closed‐off segment raised by an amount equal to the osmotic pressure of the albumin. The time of first appearance of dye from the capillary was measured. Eleven experiments were carried out and it was found that the presence of albumin doubled the time of appearance of dye from the capillary. Nine control experiments revealed no difference in the time of appearance of dye leaving a capillary perfused with the same solution under conditions of free flow or from a blocked segment. It is concluded that albumin halves the permeability of the frog mesenteric capillaries to T1824.