VARIABILITY IN THE PROLIFERATIVE RESPONSIVENESS OF CULTURED HUMAN VASCULAR SMOOTH-MUSCLE CELLS TO ALPHA-THROMBIN

alpha-Thrombin, a key enzyme of the coagulation cascade, is also a pot ent mitogen for many cell types. In the present study, the responsiven ess to alpha-thrombin of cultured human vascular smooth muscle cells ( HVSMC) derived from either vein or normal and atherosclerotic arteries was investigated. All HVSMC populations examined responded mitogenica lly to alpha-thrombin. However, the extent of this response varied bet ween different cell populations. No significant differences were obser ved between HVSMC derived from vein versus artery or atherosclerotic v ersus normal tissues. The responsiveness of a specific HVSMC culture t o alpha-thrombin was not affected by cell density and remained constan t over several passages. Unlike platelet-derived growth factor BB (PDG F-BB), alpha-thrombin did not exhibit any significant chemotactic effe cts on HVSMC or induce their anchorage independent growth in semi-soli d medium. The hypothesis that the observed variability in HVSMC respon siveness to alpha-thrombin is due to the heterogeneity of cultured HVS MC is raised and discussed.