Glycine-extended adrenomedullin exerts vasodilator effect through amidation in the rat aorta.
Human adrenomedullin (hAM) is an endogenous peptide that has potent vasodilator activity. Mature AM is biosynthesized from its intermediate form, glycine-extended AM (AM-gly), by carboxy-terminal amidation. AM-gly is generally considered to be biologically inactive but is a major molecular form in human and rat plasma. The present study demonstrated that recombinant human AM-gly (hAM-gly) elicits potent vasodilator effect on isolated rat aorta. In aortic rings, hAM-gly produced dose-dependent (0.1-100 nM) relaxation in phenylephrine-precontracted strips (pD(2) 8.4+/-0.5). The vasorelaxant potency of hAM-gly was comparable to that of hAM (pD(2) 8.6+/-0.2) but hAM-gly took a significantly (P<0.01) longer time to reach the maximal relaxation compared with hAM (T(max) 23+/-4 vs. 5+/-2 min). Vasorelaxant responses to hAM-gly were abolished by endothelial removal. N(omega)-nitro-L-arginine (L-NNA) and AM(22-52) significantly (P<0.01) reduced the vasodilator effect of hAM-gly. Furthermore, 4-phenyl-3-butenoic acid (PBA), an alpha-amidation enzyme inhibitor, significantly (P<0.05) inhibited the vasorelaxant responses to hAM-gly without any effect on the hAM-induced relaxation, suggesting the possible process of amidation in the rat aorta. We further clarified that the aorta has the ability to convert exogenous hAM-gly to mature hAM and the conversion is inhibited by PBA. These results suggest that the circulating AM-gly may play a role in regulating vascular tone and increased plasma AM-gly may be involved in the pathophysiology of cardiovascular diseases.
Cao
Yuan-Ning
YN
First Department of Internal Medicine, Miyazaki Medical College, 5200 Kihara, Kiyotake, Miyazaki 889-1692, Japan.
Kitamura
Kazuo
K
Ito
Kaoru
K
Kato
Johji
J
Hashida
Seiichi
S
Morishita
Kazuhiro
K
Eto
Tanenao
T
D053607:Adrenomedullin; D000577:Amides / Q000737:chemistry; D000818:Animals; D001011:Aorta / Q000187:drug effects* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005229:Fatty Acids, Monounsaturated / Q000494:pharmacology; D005998:Glycine / Q000737:chemistry*; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D019335:Nitroarginine / Q000494:pharmacology; D010455:Peptides / Q000737:chemistry / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D011994:Recombinant Proteins / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects*; D014665:Vasodilator Agents / Q000494:pharmacology*
D000577:Amides; D004791:Enzyme Inhibitors; D005229:Fatty Acids, Monounsaturated; D010455:Peptides; D011994:Recombinant Proteins; D014665:Vasodilator Agents; D053607:Adrenomedullin; D019335:Nitroarginine; C064180:4-phenyl-3-butenoic acid; D005998:Glycine