Excess plasma proteins as a cause of chronic inflammation and lymphoedema: biochemical estimations.

The subcutaneous tissue of rats was injected with plasma, PVP or saline. Precautions were taken to avoid immunological reactions and the release of mediators. The repeated injection of plasma proteins caused changes typical of chronic inflammation in the skin and to a much greater extent in the fascia. Coumarin significantly reduced the extent of this inflammatory reaction in the skin but not in the fascia. It increased the numbers of cells in the skin and may have stimulated them to lyse the excess protein. After 32 days, PVP injection caused some of the changes seen in chronic inflammation, but to a much lesser extent than those found with plasma. The only effect of coumarin was to reduce the water content of the skin (and hence the skin weight). It is concluded that the accumulation of excess proteins in the tissues can indeed cause chronic inflammation. In particular, chronic lymphoedema can be regarded as a form of chronic inflammation. It is also concluded that in the presence of excess protein, the benzopyrone, coumarin, is capable of stimulating cells, other than macrophages, in the skin.