A platelet factor that stimulates the proliferation of vascular endothelial cells

The effects of platelet factors on the growth of cultured porcine aortic endothelial cells were studied. Human platelet lysate stimulated the incorporation of [3H] thymidine into DNA. Gel chromatography on Sephadex G-75 revealed at least two peaks of activity on endothelial cells, the major peak being at an apparent molecular weight of 20,000. This activity was heat-labile and trypsin-sensitive, and did not stimulate the growth of fibro-blasts.