Fig. 8. ANP immunolocalisation in the ventricle of isolated amphibian heart perfused with phenylephrine (PHE) and various adrenoceptor antagonists or SB203580. Hearts were perfused under normal conditions (A) and with 50 µmol l^-1 of PHE for 0.5 min in the absence (B) or presence of either 1 µmol l^-1 prazosin (C), 1 µmol l^-1 propranolol (D) or 1 µmol l^-1 SB203580 (E). Cryosections were incubated with an antibody specific for human atrial natriuretic peptide (ANP 1-28) (1:500 dilution) and counterstained with Haematoxylin. Immunoreaction deposits for ANP were visualised with Fast Red Chromogen. Representative photographs from three independent experiments are shown. Bar, 20 µm.