An oxidized analog of alpha-human atrial natriuretic polypeptide is a selective agonist for the atrial-natriuretic-polypeptide clearance receptor which lacks a guanylate cyclase.
The differences in biological functions between alpha-human atrial natriuretic polypeptide (alpha-hANP) and its oxidized analog, MetSO-alpha-hANP, have been investigated. Analysis of the ANP receptor subtypes by affinity labeling has shown that a bovine pulmonary aortic endothelial cell line (CPAE cells) primarily expresses ANP-R1 (R, receptor) coupled to particulate guanylate cyclase, while Hela cells from human cervical carcinoma predominantly express ANP-R2, which lacks a guanylate cyclase. alpha-hANP could bind to both ANP receptor subtypes with high affinity, while MetSO-alpha-hANP showed more selective binding to ANP-R2 than to ANP-R1. The activity of MetSO-alpha-hANP for stimulation of guanylate cyclase coupled to ANP-R1 was about 520-fold less than that of alpha-hANP (median effective dose = 2.5 nM for alpha-hANP, 1.3 microM for MetSO-alpha-hANP), indicating that MetSO-alpha-hANP was a partial agonist for this receptor. While this oxidized analog could inhibit the cAMP production through ANP-R2, with 0.15 times the activity of alpha-hANP (median concentration = 0.31 nM for alpha-hANP, 2.0 nM for MetSO-alpha-hANP). In in vivo studies, the diuretic activity of MetSO-alpha-hANP was 25-100-fold less than that of alpha-hANP. In addition, MetSO-alpha-hANP could potentiate the diuretic activity of alpha-hANP that was also caused by C-ANF4-23, a specific agonist for ANP-R2. These results demonstrate that MetSO-alpha-hANP can act as an agonist more selective for ANP-R2 than for ANP-R1, both in vivo and in vitro. The relationship between receptor selectivities and the conformation of alpha-hANP or MetSO-alpha-hANP was also discussed.
Koyama
S
S
Research Laboratories, Fujisawa Pharmaceutical Co. Ltd., Osaka, Japan.
Terai
T
T
Inoue
T
T
Inomata
K
K
Tamura
K
K
Kobayashi
Y
Y
Kyogoku
Y
Y
Kobayashi
M
M
D000345:Affinity Labels; D000818:Animals; D009320:Atrial Natriuretic Factor / Q000378:metabolism* / Q000494:pharmacology; D002478:Cells, Cultured; D003432:Cross-Linking Reagents; D000242:Cyclic AMP / Q000096:biosynthesis; D004231:Diuresis / Q000187:drug effects; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism; D006162:Guanylate Cyclase / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008297:Male; D010084:Oxidation-Reduction; D051381:Rats; D011919:Rats, Inbred Strains; D017461:Receptors, Atrial Natriuretic Factor; D011956:Receptors, Cell Surface / Q000378:metabolism*
D000345:Affinity Labels; D003432:Cross-Linking Reagents; D011956:Receptors, Cell Surface; C072740:oxidized methionine-alpha-human atrial natriuretic factor; D009320:Atrial Natriuretic Factor; D000242:Cyclic AMP; D006162:Guanylate Cyclase; D017461:Receptors, Atrial Natriuretic Factor