Rats' legs and feet were studied by qualitative and quantitative electron microscopy, including mass densitometry of
protein in the tissues and in the initial lymphatics. The tissues were either normal, or had been made edematous by lymphostasis, moderate
burns, or
dextran. It was found that
Unguentum lymphaticum very greatly reduced the amount of
edema in the legs with lymphostasis. Since the concentrations of
plasma protein in the tissues and initial lymphatics, and its total amounts in the tissues were all greatly reduced, it appears that the cream's anti-lymphedematous activity is via a removal of the excess
protein. Since the macrophages were greatly increased in number by the cream (and previous work shows that selectively
poisoning these cells prevents much of the cream's effectiveness in
lymphedema), very probably it is this increase in their numbers (and possibly their individual proteolytic activities) which is how the cream causes the removal of the excess
protein--via an increased proteolysis. The cream also causes an increase in the amount of
edema in the rat-foot (after all the
injuries, including
lymphedema); however the concentration and amount of
protein in the tissues is reduced. This is consistent with an inflow of low
protein fluid, caused by a vaso-dilatation of the blood microcirculation of this rather specialized tissue. All of these characteristics are very similar to those of many of the benzo-pyrone group of drugs.