INFLUENCE OF PROTAMINE ON ADHESION, CHEMOTAXIS AND PROLIFERATION OF HUMAN VASCULAR SMOOTH-MUSCLE CELLS

It has been shown that, in streptozotocin diabetic rats, protamine-ret arded insulin administered in vivo stimulates intimal hyperplasia in b alloon-injured carotid artery. The aim of this study was to evaluate t he influence of protamine on cultured human vascular smooth muscle cel ls (hVSMC), by observing its effects on adhesion, chemotaxis and proli feration. hVSMC were isolated during abdominal surgery, cultured and u tilized at passages 6-10. We observed that protamine stimulates: 1) ce ll adhesion in the concentration range 0.04-20 mu g/ml (analysis of va riance, ANOVA, p < 0.0001); 2) cell chemotaxis in the absence of fetal calf serum (FCS) in the concentration range 1-200 mu g/ml (ANOVA, p < 0.0001) and in the presence of 1 % FCS in the concentration range 5-2 00 mu g/ml (ANOVA, p < 0.0001), further enhancing the chemotaxis induc ed by 10 % FCS in the concentration range 20-200 mu g/ml (ANOVA, p < 0 .0001); 3) cell proliferation and H-3-thymidine thymidine incorporatio n from 1 to 5 mu g/ml (ANOVA, p < 0.0001); 4) cell c-fos oncoprotein n uclear expression. We also observed that protamine effects on chemotax is, proliferation and c-fos expression are inhibited by heparin that h uman insulin stimulates cell proliferation and H-3-thymidine incorpora tion (ANOVA, p < 0.0001) at concentrations equal to or greater than 48 0 pmol/l and that these effects of insulin persist in the presence of protamine. In conclusion, protamine influences hVSMC behaviour by inte rfering with biological functions involved in atherogenesis. The conce ntrations used in this shortterm in vitro study were higher than those probably occurring in vivo in patients chronically treated by protami ne-retarded insulin preparations: further studies, therefore, are need ed to evaluate the safety of protamine as a retardant of insulin actio n in vivo.