Effects of Cl − channel blockers on endothelin-1-induced proliferation of rat vascular smooth muscle cells

Abstract

The effects of Cl − channel blockers on endothelin-1 (ET-1)-induced proliferation of rat aortic vascular smooth muscle cells (VSMC) were examined. We found ET-1 concentration-dependently increased cell count and [ 3H]-thymidine incorporation into VSMC, with EC 50 values of 24.8 and 11.4 nM, respectively. Both nifedipine and SK&F96365 inhibited 10 nM ET-1-induced [ 3H]-thymidine incorporation into VSMC with the maximal inhibitory concentrations of 1 and 10 μM, respectively. DIDS inhibited 10 nM ET-1-induced increase in cell count and [ 3H]-thymidine incorporation into VSMC in a concentration-dependent manner, whereas other Cl − channel blockers including IAA-94, NPPB, DPC, SITS and furosemide did not produce these effects. 3 μM DIDS reduced 10 nM ET-1-induced sustained increase in cytoplasmic Ca 2+ concentration ([Ca 2+] i) by 52%. Pretreatment of VSMC with 1 μM nifedipine completely inhibited the DIDS effect on 10 nM ET-1-induced [ 3H]-thymidine incorporation into VSMC and sustained increase in [Ca 2+] i, whereas pretreatment with 10 μM SK&F96365 did not completely block these effects of DIDS. DIDS did not affect ET-1-induced Ca 2+ release and 30 mM KCl-induced increase in [Ca 2+] i. Our data suggest that DIDS-sensitive Cl − channels mediate VSMC proliferation induced by ET-1 by mechanisms related to membrane depolarization and Ca 2+ influx through voltage-dependent Ca 2+ channels.