Endothelin-1 stimulates proliferation of human coronary smooth muscle cells via the ETA receptor and is co-mitogenic with growth factors

We investigated the effects of endothelin-l (ET-I) on growth of cultured hu man coronary artery smooth muscle cells (cSMC). ET-I alone stimulated DNA s ynthesis in growth-arrested cSMC as measured by [H-3]thymidine incorporatio n, with a maximum 63 +/- 23% increase above control by 10(-7) M (P < 0.05). ET-1 (10(-7) M) also stimulated increases in cyclin D1 protein levels afte r 24 h, and in absolute cell number after 4 days. Furthermore, ET-1 stimula ted protein synthesis (maximum 73 +/- 32% increase in [H-3]leucine incorpor ation by 10(-7) M (P < 0.05)), as well as triggering intracellular calcium transients in human cSMC, as visualised under fura-2 fluorescence microscop y. The selective ETA receptor antagonist BQ123 inhibited the increases in D NA synthesis, cell number, protein synthesis and intracellular calcium conc entration in response to ET-1, whereas the ET, receptor antagonist BQ788 ha d no such effects. Furthermore, the ETB agonist sarafotoxin 6c had no effec t on cSMC DNA synthesis. In addition, co-incubation of ET-1 with threshold concentrations of the growth factors, platelet-derived growth factor-BE (PD GF-BB), basic fibroblast growth factor (bFGF) and epidermal growth factor ( EGF), resulted in pronounced synergistic increases in DNA synthesis over th at observed with the factors alone. In conclusion, we have shown that ET-1 stimulates proliferation of human cSMC via the ETA receptor and is also a c o-mitogen with the growth factors tested. These findings indicate a role fo r ET-I in the development of coronary intimal hyperplasia in man. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.