Abstract
The present experiment dealt with the cell-growth promoting activity of bovine platelet vascular permeability factor (VPF) on Balb/c 3T3 fibroblasts. The author reconfirmed the previous finding that the α-granule acid extract of bovine platelets purified by means of Superose 12 contains three kinds of VPF with molecular weights of approximately 30,000, 300,000 and of greater than 450,000. In this study, sodium dodecyl sulfate polyacrylamide gel electrophoresis of the low molecular VPF revealed single band for protein of 30,000 molecular weight. The vascular permeability produced by these three VPFs in the dorsal skin of rabbits was also reconfirmed quantitatively using ^<125>I-bovine serum albumin and ultrastructurally. These VPFs stimulated cell growth of the Balb/c 3T3 fibroblasts and promoted incorporation of ^3H-thymidine into the cells. Furthermore, the growth-promoting activity of each VPF was completely inhibited by incubation with protamine sulfate and reduced by trypsin or 2-mercaptoethanol treatment. The growth activity, however, was stable after heat treatment of the factors at 100℃ for 10 min. Accordingly, VPF may play an important role in exudation and migration in acute inflammation and mesenchymal cell growth in chronic inflammation.
