The gene expression of ETAR and ETBR in early- and late-passage HSC. A: The gene expression of ETAR and ETBR in 1st and 4th passage HSC. B: the relative expression ratio of ETAR to ETBR in 1st and 4th passage HSC. HSC were plated on 25 cm2 dishes at a density of 1.0 × 105 cells/dish in DMEM containing 10% FCS. After confluence, cells were washed with PBS and placed in DMEM with 0.125% FCS for 24 hours. RNA isolation and real time PCR using SYBR Green were performed according to Material and Methods. Data were normalized to GAPDH mRNA levels. Results are given as mean ± SD (n = 5). *: p < 0.05.