Adrenomedullin (AM) (13-52), human

Analysis of responses to adrenomedullin-(13-52) in the pulmonary vascular bed of rats </h3>

"font-size:12px;">"journal"> Am J Physiol </span>"margin-right:15px;">1998 Apr;274(4):H1255-63.</span>"margin-right:15px;" title="PMID">PMID:9575929</span>"DOI">DOI:10.1152/ajpheart.1998.274.4.H1255.</span></h4>

"Abstract">The effects of "color:#e58016">human adrenomedullin-(13-52)</strong> ["color:#e58016">hADM-(13-52)</strong>] were investigated in the rat pulmonary vascular bed and in isolated rings from the rat pulmonary artery (PA). Under conditions of controlled blood flow and constant left atrial pressure when tone was increased with U-46619, injection of "color:#e58016">hADM-(13-52)</strong> produced dose-related decreases in lobar arterial pressure. Pulmonary vasodilator responses in the intact rat and vasorelaxant responses to "color:#e58016">hADM-(13-52)</strong> in rat PA rings were inhibited by NG-nitro-L-arginine methyl ester (L-NAME) and L-N5-(1-iminoethyl)-ornithine hydrochloride (L-NIO). Vasorelaxant responses to "color:#e58016">hADM-(13-52)</strong> were also inhibited by methylene blue, endothelium removal, hADM-(26-52), and iberiotoxin, whereas meclofenamate, calcitonin gene-related peptide-(8-37) [CGRP-(8-37)], glibenclamide, and apamin were without effect. Because vasorelaxant responses to NS-1619, a large-conductance Ca(2+)-activated K+ channel agonist, were not altered by L-NAME and vasorelaxant responses to acetylcholine and CGRP were not altered by hADM-(26-52), the present data suggest that ADM-(13-52) acts on a receptor in the pulmonary vascular bed that is coupled to endothelial nitric oxide release. These data suggest that this nitric oxide release may lead to guanosine 3',5'-cyclic monophosphate-dependent K+ channel activation, which produces a pulmonary vasorelaxant response through hyperpolarization of vascular smooth muscle cells. The present data suggest that ADM-(13-52) modulates receptor-mediated, but not voltage-dependent, pulmonary vascular contraction by influencing Ca2+ influx. These results suggest that the ADM fragment, "color:#e58016">hADM-(13-52)</strong>, acts as an endothelium-dependent vasodilator agent in the pulmonary vascular bed of the rat. </p></div>

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Adrenomedullin(1-52) measured in human plasma by radioimmunoassay: plasma concentration, adsorption, and storage </h3>

"font-size:12px;">"journal"> Clin Chem </span>"margin-right:15px;">1998 Mar;44(3):571-7.</span>"margin-right:15px;" title="PMID">PMID:9510864</span>"DOI">doi</span></h4>

"Abstract">We describe a specific and sensitive RIA for human adrenomedullin (AM)(1-52). The detection limit and the concentration required for 50% inhibition of binding were 0.1 and 1.2 fmol/tube, respectively. Cross-reactivities with AM(1-12), AM("color:#e58016">"color:#e58016">13-52</strong></strong>), calcitonin gene-related peptide, amylin, and other vasoactive hormones were negligible. AM immunoreactivity in normal subjects ranged from 2.7 to 10.1 pmol/L (n = 44). We investigated factors influencing the recovery and measurement of AM in the assay. Recovery of labeled AM (> 80%) was markedly higher than that of unlabeled AM (56%). Immunoreactivity of exogenous AM added to plasma decreased up to 70% over four freeze-thaw cycles, whereas endogenous AM was stable. Alkali-treated casein (1 g/L) reduced adsorption of AM to surfaces and significantly increased assay precision compared with bovine serum albumin (P < 0.0001). HPLC separation of extracted plasma verified the presence of AM(1-52). We suggest that considerable care is needed to ensure that accurate and reproducible results are obtained from studies quantifying this peptide. </p></div>

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Characterization of the adrenomedullin receptor acting as the target of a new radiopharmaceutical biomolecule for lung imaging </h3>

"font-size:12px;">"journal"> Eur J Pharmacol </span>"margin-right:15px;">2009 Sep 1;617(1-3):118-23.</span>"margin-right:15px;" title="PMID">PMID:19559019</span>"DOI">DOI:10.1016/j.ejphar.2009.06.031.</span></h4>

"Abstract">Direct labeling of linear adrenomedullin (AM) with (99m)Tc ([(99m)Tc]AM) displayed excellent selectivity for imaging the pulmonary circulation system in dogs. Hence, we investigated this particular selectivity and characterized the binding sites found in dog lungs. AM and other peptides belonging to the calcitonin peptide family, including calcitonin-gene related peptide (CGRP), adrenomedullin-2 (AM2), amylin and pro-adrenomedullin N-terminal peptide (PAMP), were prepared by solid-phase peptide synthesis. Receptor binding assays were performed by using [(125)I]AM as a radioligand on dog lung homogenates. It was found that AM bound with potent affinity, displaying in fact a high and a low affinity binding site. Moreover, competition binding assays using peptide ligands showed the following ranking for displacement: AM>AM("color:#e58016">"color:#e58016">13-52</strong></strong>)>CGRP approximately AM2> or =AM(22-52)> or =AM2(16-47)>CGRP(8-37)>amylin approximately PAMP. Thus, these results strongly suggested that the AM binding site found in dog lungs and acting as a clearance receptor is mainly the adrenomedullin AM(1) receptor subtype. The pharmacophores underlying AM(1) binding affinity and specificity were studied by determining the key amino acids, the minimal peptide fragment, and some aspects of the secondary structures. So far, it appeared that the C-terminal segment of human AM is an essential feature for binding. Also, the alpha-helix secondary structure found in the AM molecule would facilitate the ligand recognition process with the AM receptor in dog lungs. Our results demonstrated that AM or some analogs or fragments could be suitable radiopharmaceutical agents for lung imaging. </p></div>

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Structure-activity relationship of adrenomedullin, a novel vasodilatory peptide, in cultured rat vascular smooth muscle cells </h3>

"font-size:12px;">"journal"> Endocrinology </span>"margin-right:15px;">1994 Dec;135(6):2454-8.</span>"margin-right:15px;" title="PMID">PMID:7988431</span>"DOI">DOI:10.1210/endo.135.6.7988431.</span></h4>

"Abstract">Vascular smooth muscle cells (VSMC) from rat aorta possess specific receptors for a novel potent vasorelaxant peptide, adrenomedullin (AM). To elucidate its receptor coupling to guanine nucleotide-binding stimulatory protein and the structural requirement of the AM molecule to its vascular receptors, we have studied the effects of guanine nucleotides on [125I]human (h) AM binding and adenylate cyclase activity in cultured rat VSMC, and the effects of various synthetic hAM analogs on [125I]hAM binding and the cAMP response. Guanosine 5'-O-(3-thiotriphosphate) dose dependently inhibited [125I]hAM binding to rat VSMC membranes. hAM stimulated adenylate cyclase activity, and its effect was additive with GTP. hAM-induced cAMP formation was abrogated by pretreatment with cholera toxin, but not by that with pertussis toxin. Intact hAM-(1-52)-NH2 and N-terminal truncated derivatives [hAM-("color:#e58016">"color:#e58016">13-52</strong></strong>)-NH2, hAM-(16-52)-NH2] almost equally inhibited [125I]hAM binding and stimulated cAMP formation, whereas removal of C-terminal Tyr52 residue [hAM-(1-51)-NH2] remarkably decreased receptor-binding activity and the cAMP response. The effects of hAM-(1-52)-OH, hAM-(1-51)-OH, and a linear hAM analog ([carbamoylmethyl-Cys16,21]hAM-NH2) were far less potent on receptor binding and the cAMP response than that of hAM-(1-52)-NH2. The C-terminal fragment [hAM-(33-52)-NH2] and the N-terminal fragment [hAM-(1-10)-OH] had neither receptor-binding nor adenylate cyclase activity. hAM-(22-52)-NH2 had no agonistic effect, but showed an antagonistic effect on the hAM-induced cAMP response. These data suggest that vascular AM receptors are functionally coupled to adenylate cyclase via guanine nucleotide-binding stimulatory protein. Studies of the structure-activity relationship of hAM revealed that the cyclic structure formed by the disulfide bridge and amidation of the C-terminal residue of the AM molecule are critical for receptor binding and subsequent cAMP generation and suggest that the C-terminal fragment hAM-(22-52)-NH2 may be an antagonist for vascular AM receptors. </p></div>

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Pulmonary vasodilation to adrenomedullin: a novel peptide in humans </h3>

"font-size:12px;">"journal"> Am J Physiol </span>"margin-right:15px;">1995 Jun;268(6 Pt 2):H2211-5.</span>"margin-right:15px;" title="PMID">PMID:7611471</span>"DOI">DOI:10.1152/ajpheart.1995.268.6.H2211.</span></h4>

"Abstract">The present study investigates the effects of human adrenomedullin (ADM) on the pulmonary vascular bed of isolated, blood-perfused rat lung. Because pulmonary blood flow and left atrial pressure were constant, changes in pulmonary arterial pressure directly reflect changes in pulmonary vascular resistance. Under conditions of resting (low) pulmonary vasomotor tone, intra-arterial bolus injections of ADM-(1-52) and two truncated sequences of ADM-(1-52) [ADM-(1-12) and ADM-("color:#e58016">"color:#e58016">13-52</strong></strong>)] did not alter pulmonary arterial pressure. When pulmonary vasomotor tone was increased by U-46619, a thromboxane A2 mimic, intra-arterial bolus injections of ADM-(1-52) and ADM-("color:#e58016">"color:#e58016">13-52</strong></strong>) at similar doses produced similar, dose-dependent reductions in pulmonary arterial pressure. On a molar basis, ADM-(1-52) had greater pulmonary vasodilator activity than isoproterenol. In contrast, ADM-(1-12) had no activity. When pulmonary vasomotor tone was actively increased to the same level using KCl, the pulmonary vasodilator activity of ADM-("color:#e58016">"color:#e58016">13-52</strong></strong>) was decreased 10-fold. The present data demonstrate that ADM-(1-52) dilates the pulmonary vascular bed and suggest that the pulmonary vasodilator activity of ADM is greater on pulmonary blood vessels preconstricted through a receptor-dependent mechanism. Because meclofenamate, nitro-L-arginine methyl ester, methysergide, BW A-1433U83, U-37883A,