NOVEL SITES OF ADRENOMEDULLIN GENE-EXPRESSION IN MOUSE AND RAT-TISSUES

Adrenomedullin (AM) was originally identified in pheochromocytoma tiss ue and was characterized as a hypotensive peptide. The tissue distribu tion and cellular localization of AM messenger RNA (mRNA) were determi ned in mouse and rat tissues by in situ hybridization. Three probes we re used: two nonoverlapping probes to the pro-AM N-terminal 20 peptide (PAMP) and AM peptide regions of mouse pro-AM, and a larger complemen tary DNA (cDNA) probe spanning both the PAMP- and AM peptide-coding re gions. The most intense expression of AM mRNA was in endometrium and e pithelial cells lining the uterus and mouse adrenal medulla. Moderate levels of expression were detected in kidney glomerulus and cortical d istal tubules, ovarian corpus luteum and follicles, epithelial cells l ining the bronchioles, cardiac atrium and ventricle, posterior pituita ry (particularly in female rats), stomach, small intestine (microvilli , mucosa and submucosa), spleen, and pancreas. Lower levels were obser ved in pulmonary alveoli, anterior pituitary, and submandibular gland. No expression was detected in the testis, thymus, skeletal muscle, or liver. The localization of AM mRNA in epithelial cells lining the ute rus, bronchioles, and gastrointestinal tract indicates novel roles for AM, possibly as an antimicrobial agent. The strong expression of AM i n uterus, ovary, and posterior pituitary suggests that AM plays a role in female reproduction.