Absence of Capillary Permeability Response in Rats to Dextran and Egg-White

Abstract

Intradermal dextran and ovomucoid fail to increase capillary permeability in rats resistant to intraperitoneal dextran although intradermal histamine, 5-HT and compound 48/80 are as effective as in control rats. When the skin of control rats is depleted of its histamine, intradermal dextran and ovomucoid are first ineffective but later increase capillary permeability although the skin histamine remains low. Chronic treatment of control rats with intraperitoneal dextran (which only slightly reduces both the skin histamine and 5-HT) prevents the local dextran and ovomucoid responses but does not affect those of compound 48/80, histamine and 5-HT. It is concluded that intradermal dextran and ovomucoid increase capillary permeability in rats by a mechanism involving substances other than histamine and 5-HT, and that this mechanism is absent in rats which do not respond to intraperitoneal dextran.