Permeability-increasing activity in hereditary angioneurotic edema plasma. II. Mechanism of formation and partial characterization.

Plasma from persons with hereditary angioneurotic edema readily developed the capacity to increase vascular permeability and to induce the isolated rat uterus to contract. Both activities resided in a small, heat-stable molecule that was apparently a polypeptide. Crude preparations of the polypeptide were inactivated during incubation with trypsin. They also failed to produce pain and erythema, but caused markedly increased vascular permeability in human skin. These characteristics differ from those of bradykinin, from which crude preparations of the polypeptide could also be distinguished by electrophoretic mobility and paper chromatographic behavior. Proof that the polypeptide is truly different from bradykinin must await its further purification. Histamine played no role in the activities observed. Although the enzymes functioning to release the permeability factor and kinin activities in hereditary angioneurotic edema plasma were not clearly defined, one or more plasma enzymes other than C'1 esterase presumably participated either in conjunction with C'1 esterase or in pari passu events to release the polypeptide mediating these activities.