Proadrenomedullin NH2-terminal peptide (PAMP)(12-20) has vasodepressor activity in the rat and cat

Effect of vasoactive peptides in Tetrahymena: chemotactic activities of adrenomedullin, proadrenomedullin N-terminal 20 peptide (PAMP) and calcitonin gene-related peptide (CGRP)

Adrenomedullin (AMD), proadrenomedullin N-terminal 20 peptide (PAMP) and calcitonin gene-related peptide (CGRP) were studied for chemotaxis, chemotactic selection and G-actin/F-actin transition in Tetrahymena. The aim of the experiments was to study the effects of two different peptides encoded by the same gene compared to a peptide related to one of the two, but encoded by a different gene, at a low level of phylogeny. The positive, chemotactic effect of ADM and the strong negative, chemorepellent effect of PAMP suggest that in Tetrahymena, the two peptides elicit their chemotactic effects via different signalling mechanisms. The complexity of swimming behaviour modulated by the three peptides underlines that chemotaxis, chemokinesis and some characteristics of migratory behaviour (velocity, tortuosity) are working as a sub-population level complex functional unit. Chemotactic responsiveness to ADM and CGRP is short-term, in contrast to PAMP, which as a chemorepellent ligand, has the ability to select sub-populations with negative chemotactic responsiveness. The different effects of ADM and PAMP on the polymerization of actin networks show that the microtubular structure of cilia is more essential to chemotactic response than are transitions of the actin network. The results draw attention to the characteristic effects of vasoactive peptides at this low level of phylogeny.

Cell and molecular biology of the multifunctional peptide, adrenomedullin

Adrenomedullin (AM) is a recently discovered regulatory peptide involved in many functions including vasodilatation, electrolyte balance, neurotransmission, growth, and hormone secretion regulation, among others. This 52-amino acid peptide is expressed by specific cell types in many organs throughout the body. A complex receptor system has been described for AM; it requires at least the presence of a seven-transmembrane-domain G-protein-coupled receptor, a single-transmembrane-domain receptor activity modifying protein, and a receptor component protein needed to establish the connection with the downstream signal transduction pathway, which usually involves cyclicAMP. In addition, a serum-binding protein regulates the biological actions of AM, frequently by increasing AM functional attributes. Changes in levels of circulating AM correlate with several critical diseases, including cardiovascular and renal disorders, sepsis, cancer, and diabetes. Whether AM is a causal agent, a protective reaction, or just a marker for these diseases is currently under investigation. New technologies seeking to elevate and/or reduce AM levels are being investigated as potential therapeutic avenues.

Selective inhibition of nicotinic cholinergic receptors by proadrenomedullin N-terminal 12 peptide in bovine adrenal chromaffin cells

We studied whether a novel proadrenomedullin derived peptide was present and what was its physiological function in cultured bovine adrenal chromaffin cells. We found a high level of proadrenomedullin N-terminal 12 peptide (PAMP-12) which consists of a peptide from 9th amino acid to 20th amino acid of proadrenomedullin N-terminal 20 peptide (PAMP-20). PAMP-12 was released from the cells along with catecholamine upon stimulation of nicotinic cholinergic receptors. When PAMP-12 was added in the incubation medium, this peptide inhibited nicotinic receptor-mediated catecholamine release and influx of Na(+) and Ca(2+) into the cells. PAMP-12 did not affect catecholamine release evoked by histamine or by depolarization by high concentration of potassium. PAMP-12 also inhibited synthesis of catecholamines as well as the activation of tyrosine hydroxylase by nicotinic stimulation. Thus, PAMP-12 is an endogenous peptide that regulates release and synthesis of catecholamines by acting on nicotinic cholinergic receptors in an autocrine manner in adrenal chromaffin cells.

Comparison of vasodilator potency of adrenomedulling and proadrenomedullin N-terminal 20 peptide in human

Adrenomedullin (ADM) and proadrenomedullin N-terminal peptide (PAMP), both of which are derived from preproadrenomedullin, are reported to have a potent hypotensive effect in animals. However, no data are available concerning the vasodilatory potency of PAMP or comparing this potency to that of ADM in human vasculature. We examined the effects of intra-arterial infusion of graded doses of ADM (1.25, 2.5, 5.0 and 7.5 pmol/min per 100 ml of tissue) and PAMP (125, 250, 500, 750 and 1000 pmol/min per 100 ml of tissue) on total forearm blood flow and forearm skin blood flow in 11 healthy subjects. ADM increased total forearm blood flow from 2.9 +/- 0.4 to 8.6 +/- 1.1 ml/min per 100 ml (p < 0.01), and skin blood flow from 0.07 +/- 0.02 to 0.14 +/- 0.03 volts (p < 0.01). In contrast to this potent vasodilatory effect, a significant rise in forearm skeletal blood flow was seen only in response to the maximum dose of PAMP (from 2.7 +/- 0.5 to 5.3 +/- 1.0 ml/min per 100 ml; p < 0.01). In addition, PAMP had no significant vasoactive effect on skin blood flow (from 0.06 +/- 0.02 to 0.09 +/- 0.03 volts; NS). In conclusion, the skeletal muscle vasodilator potency of PAMP is less than one hundredth of that of ADM in human forearm. Given its weak dilator potency, it seems unlikely that PAMP alone could significantly regulate resistance vessel tone as a circulating hormone in humans.

Increased plasma proadrenomedullin N-terminal 20 peptide in patients with essential hypertension

The novel hypotensive peptide, proadrenomedullin N-terminal 20 peptide (PAMP), is processed from the adrenomedullin precursor. Recently, we identified PAMP-12 [PAMP(9-20)] from the porcine adrenal medulla as a major endogenous and biologically active peptide. Using a new, sensitive radioimmunoassay which recognizes the C-terminal region of PAMP-20 [PAMP(1-20)], we investigated the role of PAMP in patients with essential hypertension who had normal renal function, and whether PAMP-12 is present in humans. The mean PAMP plasma concentration, like that of adrenomedullin, was significantly higher in hypertensive [1.51 fmol/mL, standard error of the mean (SEM) 0.09 fmol/mL] than normotensive participants (1.08 fmol/mL, SEM 0.05). The increase in plasma PAMP concentration in patients with organ damage accompanied by hypertension was significantly higher than that in patients without organ damage. The PAMP concentration had a significant positive correlation with mean blood pressure and adrenomedullin concentration. The immunoreactive PAMP in human tissue and plasma was characterized by reverse-phase high-performance liquid chromatography. PAMP-12, as well as PAMP-20, was abundant in the phaeochromocytoma tissue. These findings suggest that PAMP plays some pathophysiological role against the development of essential hypertension.