Characterization of vascular permeability-increasing component isolated from solid tumors and the effect of highly polymerized dextran sulfate on its activity.

Increase in vascular permeability is usually seen at the growth site of a tumor implant in murine dermal tissue. Increased vascular permeability was inducible by the subcutaneous injection of a solid tumor extract rich in protein precipitable at 20-50% saturation of ammonium sulfate. The vascular permeability-increasing activity of the tumor extract was reducible in the presence of highly polymerized dextran sulfate (DS-500) which showed a strong anticomplementary activity, but not by other substances such as dextran sulfate with a low molecular weight, non-sulfated dextran, chondroitin sulfate or heparin. As the tumor extract includes gamma-globulins in aggregated or bound form and adsorbs complements, it is probable that the aggregated gamma-globulins increase vascular permeability by triggering the complement activation system in the skin. DS-500 might antagonize the process.