atrial-natriuretic-factor and 1-10-phenanthroline

Pulmonary vascular relaxant effects of the 28-amino acid atrial natriuretic peptide and atriopeptins I, II and III (21, 23 and 24 amino acid peptides, respectively) were studied in isolated blood vessels and in perfused rat lungs. In isolated tissue studies, intrapulmonary arteries were more responsive to the relaxant effects of atrial peptides than the main pulmonary artery or aorta. In perfused lung preparations, each of the four atrial peptides produced dose-dependent pulmonary vasodilation of PGF2 alpha or hypoxia-induced pulmonary vasoconstriction. Atriopeptin I was the least potent pulmonary vasodilator peptide in all studies. Pretreatment of perfused lungs with various peptidase inhibitors, including the angiotensin converting enzyme inhibitors, captopril and MK-521, the carboxypeptidase inhibitor, 1,10-phenanthroline, and the aminopeptidase inhibitor, bestatin, variably potentiated the pulmonary vasodilator activities of the atrial peptides. The results demonstrate that atrial peptides released from the right heart into the pulmonary circulation can have potent vasorelaxant effects in the pulmonary vascular bed and further suggest that upon passage through the lung atrial peptides may undergo metabolic degradation that alters their pulmonary vasodilator activities.

Topics: Aminopeptidases; Angiotensin-Converting Enzyme Inhibitors; Animals; Atrial Natriuretic Factor; Carboxypeptidases; Drug Interactions; Enalapril; In Vitro Techniques; Leucine; Lisinopril; Male; Perfusion; Phenanthrolines; Pulmonary Artery; Rats; Rats, Inbred Strains; Vasodilator Agents

Multiple forms of atrial natriuretic factor receptor have been identified in human placental membranes. Atrial natriuretic factor binds specifically to placental membranes and the binding activity could be solubilized using non ionic detergent, Triton X-100. Binding to the detergent solubilized preparation was inhibited 80% by the addition of 0.5 M sodium chloride. Affinity cross-linking analysis indicated that this binding was associated with a single protein band of molecular weight 170-kDa. On the other hand, if sodium chloride was added together with a chelator, o-phenanthroline, ANF binding to this preparation was stimulated 300%. Binding under these conditions was not to the 170-kDa protein but was associated with a broad band in the region of 100/110-kDa and a minor band at 200-kDa. These observations clearly indicated that in human placental membranes, atrial natriuretic factor binds to distinctly different molecular species depending on the presence or absence of certain ions and chelators. The two types of binding could be conveniently assayed in the presence of each other by elimination or inclusion of sodium chloride and o-phenanthroline in the assay system.

Topics: Atrial Natriuretic Factor; Electrophoresis, Polyacrylamide Gel; Humans; Membranes; Molecular Weight; Octoxynol; Phenanthrolines; Placenta; Polyethylene Glycols; Receptors, Atrial Natriuretic Factor; Receptors, Cell Surface; Sodium Chloride; Solubility