Studies on the vascular permeability factor of bovine and human platelets.

The vascular permeability factors (VPFs) of bovine and human platelets were studied on the vascular permeability activity in the skin of unanesthetized rabbits. By continuous Urografin or sucrose density gradient method, subcellular organelles were separated from both bovine and human platelets as four fractions. Acid extract prepared from each fraction was used as a provocative for the production of inflammation. After intradermal injection, the alpha-granule extract alone provoked an obvious vascular permeability activity. In skin sites responding to the injection, high concentration of the bovine VPF induced a monophasic response with time, though both human and low concentration of bovine VPFs brought about nearly the same biphasic response. On quantitative analysis of the vascular permeability activity, chromatoscanner method was applied for the first time to the estimation of exuded dye. It was confirmed that the method attains to satisfactory results corresponding to those by the common dye-extraction method. We assume that the bovine and human platelets may play a role in inflammation by releasing the VPF during the aggregation and adhesion of the cells to each other as well as to the endothelium in association with migration.