The Gradient of Vascular Permeability

Abstract

The recognition that permeability increases progressively along the capillaries of voluntary muscle (1) has led us to study the state of affairs in other organs. An exceedingly pronounced gradient is demonstrable in the skin of the frog, and the small cutaneous venules are even more permeable than the adjoining portion of the capillaries (2). Because of the importance of mammalian skin in water storage and regulation, we have proceeded to study this organ. The skin of the albino mouse was chosen for the purpose because the spread of dyes from the blood can be followed with special ease in it. The Escape of Dyes from the Blood into the Skin of the BodyIn preliminary tests vital dyes of known diffusibility were injected into a tail vein of unanesthetized animals which were decapitated shortly after. The skin was found to color evenly with rapidly diffusible pigments, whereas with poorly diffusible ones, such as are especially suited to disclose local differences in vascular permeability, there was to be seen a deep staining of the tissue through which the small venules coursed, before any general coloration of the corium had taken place. The phenomenon was visible only when a skin flap was studied from its under side and even then ordinarily the subcutaneous fat prevented a clear view. To do away with it mice were kept on a reduced ration until they had become thin. They yielded pictures that were highly informative.

The Gradient of Permeability of the Skin Vessels as Influenced by Heat, Cold, and Light

“…Under normal circumstances there are many regions in the skin of the ear of the rabbit, cat, and dog through which blood flows almost not at all. The same has been found true of the mouse (1). After a dye injection into this animal one observes not a few venules in normal ears containing almost unstained blood, the reason being that none has got through most of the capillaries of the web that they drain; and needless to say, the tissue surrounding such venules remains unstained.…”

“…Only under such circumstances did an approximately even staining of the tissue take place. In the persistence of the gradient despite lesser but still considerable degrees of vascular disturbance one can find a new reason besides those already advanced (1,(6)(7)(8)(9) for the assumption that the gradient depends upon the structure of the vessel wall, not on functional conditions. Its practical disappearance when this wall is badly damaged proves that it cannot be the result of local differences in the extravascular fabric, a possibility brought up in a preceding paper.…”

“…Nevertheless, the comparison of the experimental and control ears was always carried out very rapidly. The technic of the lighting has been described in a previous paper (1). 431…”

“…Patching takes place far more quickly than in the control organ; and the patches are more numerous. Also in the case of pontamine blue diffuse coloration develops concurrently with the patching as never happens with this poorly diffusible pigment under normal conditions, I though with highly diffusible dyes it is a regular occurrence (1). Increased blood flow, heightened intracapillary pressure, and the capillary dilatation of active hyperemia are doubtless responsible for the phenomenon.…”

A Theoretical Study of Restricted Convention‐Diffusion as Applied to Blood‐Tissue Barrier Exchange

“…Albumin is known to pass the capillary walls with difficulty. Assuming reabsorption at the venous end of the capillaries, which probably is more permeable than the arterial end (Smith andRous 1931, Hauck andSchroer 1969) although still not permeable to proteins to a visible extent (Wiederhielm 1968), the operational reabsorption pore radius ought not to be larger than about 6 nm. Values between 4 and 6.5 nm are tested in the model.…”