Studies on biochemical analysis of vascular permeability factors from bovine and human platelet α-granules

Vascular permeability factor (VPF) was extracted from human and bovine platelet α-granules and partially purified by ion exchange and gel filtration chromatographies. Human and bovine VPFs were cationic proteins, and these isoelectric points were 9.2 and 8.8, respectively, by electric-focusing technique. The human VPF was mainly localized into the fraction of approximate Mw. of 30, 000 by gel filtration (G-75). On the other hand, the bovine VPF was localized into the fraction, an estimated Mw. 140, 000 by gel filtration (S-300). After purification by G-75 gel filtration, permeability activity of bovine VPF was 1, 300μl/mg of protein. The stability of VPFs was also studied after a variety of treatments. These VPFs were activated at 50-60°C and extremely stable to a temperature up to 80°C. They were also stable on exposure to acid or alkaline (pH 1.3-12), but inactivated by pepsin or 2-mercaptoethanol treatment.