ADRENOMEDULLIN RECEPTOR EXPRESSION IN HUMAN LUNG AND IN PULMONARY TUMORS

Adrenomedullin (AM) is a multifunctional regulatory peptide that stimu lates cyclic AMP production in many target tissues and is highly expre ssed in the lung. Analysis of the distribution of the recently cloned AM receptor (AM-R) by non-radioactive in situ hybridization revealed a bundant expression in the basal cells of the airway epithelium and Typ e II pneumocytes. The expression of AM-R in the two cell types involve d in epithelial regeneration of the lung suggests that AM may be relev ant in such functions as organ development, wound repair, and epitheli al turnover. AM-Rs are also synthesized in vivo and in vitro by a vari ety of tumor cells that also express the ligand, suggesting the existe nce of an autocrine loop that may be involved in tumor growth stimulat ion. The present findings suggest that the AM/AM-R regulatory system p lays a major role in respiratory physiology and lung carcinogenesis an d that new functions for AM remain to be identified.