title: Atrial natriuretic peptide degradation by CPA47 cells: evidence for a divalent cation-independent cell-surface proteolytic activity.
abstract: Atrial natriuretic peptide (ANP) is rapidly cleared and degraded in vivo. Nonguanylate-cyclase receptors (C-ANPR) and a metalloproteinase, neutral endopeptidase (EC 3.4.24.11) (NEP 24.11), are thought to be responsible for its metabolism. We investigated the mechanisms of ANP degradation by an endothelial-derived cell line, CPA47. CPA47 cells degraded 88% of 125I-ANP after 1 h at 37 degrees C as determined by HPLC. Medium preconditioned by these cells degraded 41% of the 125I-ANP, and this activity was inhibited by a divalent cation chelator, EDTA. Furthermore, a cell-surface proteolytic activity degraded 125I-ANP in the presence of EDTA when receptor-mediated endocytosis was inhibited either by low temperature (4 degrees C) or by hyperosmolarity at 37 degrees C. The metalloproteinase, NEP 24.11, is unlikely to be the cell-surface peptidase because 125I-ANP is degraded by CPA47 cells at 4 degrees C in the presence of 5 mM EDTA. These data indicate that CPA47 cells can degrade ANP by a novel divalent cation-independent cell-surface proteolytic activity.
authors.affiliation: Biomedical Operations and Research Branch, NASA Johnson Space Center, Houston, TX 77058.
authors.forename: S J
authors.initials: SJ
authors.lastname: Frost
authors.forename: Y M
authors.initials: YM
authors.lastname: Chen
authors.forename: P A
authors.initials: PA
authors.lastname: Whitson
mesh_terms: D009320:Atrial Natriuretic Factor / Q000378:metabolism*; D002413:Cations, Divalent; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D004492:Edetic Acid; D006801:Humans; D006868:Hydrolysis; D007457:Iodine Radioisotopes; D007700:Kinetics; D015260:Neprilysin / Q000378:metabolism; D009994:Osmolar Concentration; D017461:Receptors, Atrial Natriuretic Factor / Q000378:metabolism
chemical_list: D002413:Cations, Divalent; D007457:Iodine Radioisotopes; D009320:Atrial Natriuretic Factor; D004492:Edetic Acid; D015260:Neprilysin; D017461:Receptors, Atrial Natriuretic Factor