[Show abstract][Hide abstract] ABSTRACT: Adrenomedullin (AM) is a potent vasodilator peptide present in the lung of mammals where it is expressed mainly in the columnar epithelium and alveolar macrophages. AM increases the secretion of phosphatidylcholine by type II pneumocytes, which suggests a role as an autocrine modulator of surfactant secretion. In this study we show the expression of an AM-like protein in the lung of the pigeon, Columba livia. Using an antibody against its human ortholog, AM-like immunoreactivity was found to be associated with membranous structures of the multivesicular bodies of type II pneumocytes. We also studied the differential expression of AM-like peptide in the lung of pigeons exposed to polluted city air vs cleaner countryside conditions and found that AM-like expression was higher in city animals. Similar results were obtained in an experimental study in which pigeons were exposed to increasing concentrations of a single pollutant, ozone. Taken together, our findings support the implication of AM in the response of type II pneumocytes to air pollutants.
Journal of Histochemistry and Cytochemistry 07/2005; 53(6):773-80. DOI:10.1369/jhc.4A6498.2005 · 2.40 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Adrenomedullin (AM) immunoreactivity has been found in granules of the glomus (type I) cells of the carotid bodies in rats. The identity of these cells was ascertained by colocalization of immunoreactivities for AM and tyrosine hydroxylase in their cytoplasm. Exposure of freshly isolated carotid bodies to synthetic AM resulted in a concentration- and time-dependent degranulation of glomus cells as measured by dopamine (DA) release. DA release reached a zenith 30 min after exposure to AM (94.2% over untreated controls). At this time-point, the response to AM was similar to the one elicited by 5 min of exposure to 100 mM K+. Nevertheless, injection of 1 micro l 60 nM AM/g body weight into the tail vein of the rats did not induce statistical differences in DA release from the carotid bodies. Exposure of the oxygen-sensitive cell line PC-12 to hypoxia elicited an increase in AM mRNA expression and peptide secretion into serum-free conditioned medium. Previous data have shown that elevation of AM expression under hypoxia is mediated through hypoxia-inducible factor-1, and that exposure of chromaffin cells to AM results in degranulation. All these data suggest that AM is an important autocrine regulator of carotid body function.
Journal of Endocrinology 02/2003; 176(1):95-102. · 3.59 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Adrenomedullin is a vascular tissue peptide and a member of the calcitonin family of peptides, which includes calcitonin, calcitonin-gene-related peptide (CGRP) and amylin. Its many biological actions are mediated via CGRP type 1 (CGRP(1)) receptors and by specific adrenomedullin receptors. Although the pharmacology of these receptors is distinct, they are both represented in molecular terms by the type II family G-protein-coupled receptor, calcitonin-receptor-like receptor (CRLR). The specificity here is defined by co-expression of receptor-activity-modifying proteins (RAMPs). CGRP(1) receptors are represented by CRLR and RAMP1, and specific adrenomedullin receptors by CRLR and RAMP2 or 3. Here we discuss how CRLR/RAMP2 relates to adrenomedullin binding, pharmacology and pathophysiology, and how chemical cross-linking of receptor-ligand complexes in tissue relates to that in CRLR/RAMP2-expressing cells. CRLR, like other type II family G-protein-coupled receptors, signals via G(s) and adenylate cyclase activation. We demonstrated that adrenomedullin signalling in cell lines expressing specific adrenomedullin receptors followed this expected pattern.
Biochemical Society Transactions 09/2002; 30(4):432-7. · 3.24 Impact Factor
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