Degradation and inactivation of rat atrial natriuretic peptide 1-28 by neutral endopeptidase-24.11 in rat pulmonary membranes.
Atrial natriuretic peptide (ANP), a 28-residue peptide with cardiovascular and renal effects, is rapidly cleared from the circulation. Beside renal clearance, an extra-renal metabolism by the enzyme neutral endopeptidase-24.11 (NEP-24.11) has been proposed, since specific NEP-24.11-inhibitors increase endogenous plasma-ANP. NEP-24.11 is present in rat lung but its significance for ANP hydrolysis within the lung is unclear. The aim of this study was to investigate a possible degradation of rat ANP in a membrane preparation from rat lung. Hydrolysis products of ANP were separated by HPLC and further characterized by a pulmonary artery bioassay, by radioimmunoassay with different antisera, by peptide sequencing and by masspectrometry. Rat pulmonary membranes degraded ANP to one main metabolite lacking biological activity and with poor cross-reactivity to an antiserum recognising the central ring-structure of the peptide. Formation of the hydrolysis product was prevented by the NEP-24.11-inhibitor phosphoramidon (1 microM). Peptide sequencing of the metabolite revealed a cleavage between Cys7 and Phe8, which was confirmed by mass-spectrometry. The metabolite had an HPLC elution time identical to that of the product formed by purified porcine NEP-24.11. These findings suggest that ANP is metabolized and inactivated by endopeptidase-24.11 in rat lungs, the first organ exposed to ANP released from the heart.
Lindberg
B F
BF
Department of Clinical Pharmacology, University Hospital of Lund, Sweden.
Bengtsson
H I
HI
Lundin
S
S
Andersson
K E
KE
D000595:Amino Acid Sequence; D000818:Animals; D009320:Atrial Natriuretic Factor / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000494:pharmacology; D001681:Biological Assay; D002851:Chromatography, High Pressure Liquid; D006020:Glycopeptides / Q000494:pharmacology; D006868:Hydrolysis; D066298:In Vitro Techniques; D008168:Lung / Q000201:enzymology*; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D015260:Neprilysin / Q000378:metabolism*; D011651:Pulmonary Artery / Q000187:drug effects / Q000502:physiology; D011817:Rabbits; D011863:Radioimmunoassay; D051381:Rats; D017207:Rats, Sprague-Dawley
D006020:Glycopeptides; D009320:Atrial Natriuretic Factor; D015260:Neprilysin; C008890:phosphoramidon