Respective roles of kallikrein and endopeptidase 24.11 in the metabolic pathway of atrial natriuretic peptide in the rat.
The metabolism of atrial natriuretic peptide (ANP) and Cys-105-Phe-106-cleaved ANP (ANP) was studied during constant infusion of 125I-labelled peptides in rats. Analysis of circulating radioactivity indicated rapid clearance of ANP and ANP', with mean half-lives of 0.42 and 1.04 min respectively. H.p.l.c. fractionation of plasma taken during the infusion of labelled ANP revealed the presence of three radioactive fragments, the major one co-eluting with 125I-ANP'. These fragments correspond to cleavage products previously found to be generated in vitro by the action of endopeptidase 24.11 (E-24.11). On evaluating the effects of peptidase inhibitors, a significant increase in the half-life of ANP was observed with phosphoramidon (t1/2 7.8 min) and aprotinin (t1/2 5.4 min). A maximal inhibition of ANP degradation was obtained when both inhibitors were given simultaneously (t1/2 15 min). In blood samples taken during infusion of 125I-ANP and phosphoramidon, the intact peptide accounted for more than 90% of total circulating radioactivity, and no cleavage product was present in detectable amounts. Phosphoramidon had no effect on the metabolism of infused ANP'. In contrast, when 125I-ANP' was infused together with aprotinin, the rate of degradation of the infused peptide was reduced by more than 80%. It is proposed that two different peptidase activities, E-24.11 and a kallikrein-like proteinase, are responsible for the cleavage of ANP in the circulation. The Cys-Phe-cleaved ANP would in turn be degraded by kallikrein and not by E-24.11.
Laboratoire Pluridisciplinaire de Recherche Expérimentale Biomédicale, Faculté de Médecine, Université Libre de Bruxelles, Brussels, Belgium.
Y
Y
Vanneste
S
S
Pauwels
L
L
Lambotte
A
A
Michel
R
R
Dimaline
M
M
Deschodt-Lanckman
D000595:Amino Acid Sequence; D000818:Animals; D007611:Aprotinin / Q000494:pharmacology; D009320:Atrial Natriuretic Factor / Q000378:metabolism*; D006020:Glycopeptides / Q000494:pharmacology; D007457:Iodine Radioisotopes; D007610:Kallikreins / Q000378:metabolism*; D008969:Molecular Sequence Data; D015260:Neprilysin / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism; D051381:Rats; D013820:Thermolysin / Q000037:antagonists & inhibitors
D006020:Glycopeptides; D007457:Iodine Radioisotopes; D010446:Peptide Fragments; D009320:Atrial Natriuretic Factor; D007611:Aprotinin; D007610:Kallikreins; D015260:Neprilysin; D013820:Thermolysin; C008890:phosphoramidon