(A), HUVECs responded to SCF with significant synthesis of ET3 (left panel) and secretion of ET3 in media (right panel). (B), WM793 melanoma cells responded to SCF with significant synthesis (left panel) and secretion of ET3 in serum-free culture medium (right panel). (C), In situ IHC. Top panels, control WM793 cells without SCF stimulation, more than 95% cells exhibited completely negative staining for BigET3, ECE-1, or ET3. Lower panels, WM793 cells after stimulation with SCF (100 ng/ml) for 24 hours. ETBR expression remained unchanged (a and e). Robust induction of BigET3 (f), ECE-1 (g), ET3 (h), and clusters of sub-membranous ET3 before secretion (h, open arrows) are observed in more than 95% of cells comparing to the respective controls (b, c, d).