Effect of ET-1 on DNA synthesis and proliferation in HSC. A: Effect of ET-1 on DNA synthesis of 1st passage HSC. BrdU incorporation into DNA was measured in 8 × 103 HSC during 48 h and at different concentrations of FCS. Absorbance values of controls were set as 100% for each concentration of FCS and values normalized to the respective control culture levels. Results were means ± SD (n = 8). There was no effect of ET-1 on the proliferation of 1st passage HSC. B: Inhibitory effect of ET-1 on the proliferation of 4th passage HSC. BrdU incorporation into DNA was measured in 8x103 HSC during 48 hours at different concentrations of ET-1 or the ETBR agonist S6c with 10% FCS. The ETAR antagonist, BQ123, or the ETBR antagonists, BQ788, were added at 10-6 M in the presence of 10-6 M of ET-1. Results are given as mean ± SD (n = 8). Absorbance values of controls were set as 100% and values for cultures under the influence of each concentration of ET-1 or S6c are shown. *p < 0.05, **p < 0.01 vs control, ## p < 0.01 vs ET -1 10-6 M.