Figure 2. Competition assay: specificity of antibodies used. Preabsorption of ET-1 and ETB-receptor antibody with a 1,000-fold molar excess of the corresponding peptide confirms the specificity of the respective antibodies. Competition with the ETA-receptor-specific peptide was unsatisfactory; an unspecific staining by this antibody cannot be excluded. However, both ETA-receptor antibodies derived from different suppliers were consistent in terms of their staining pattern in pancreatic islets. Bar = 50 μm; same magnification in all pictures.