EXPRESSION OF ADRENOMEDULLIN AND ADRENOMEDULLIN MESSENGER-RNA IN ECTOPIC ACTH-SECRETING TUMORS

Objective: To study the expression of adrenomedullin, a potent vasodil ator peptide originally isolated from a pheochromocytoma, in ectopic A CTH-secreting tumors. Methods: Tumor tissue concentrations of adrenome dullin, calcitonin gene-related peptide, neuropeptide Y, endothelin-1, corticotropin-releasing hormone and ACTH were measured in three ectop ic ACTH-secreting tumors by RIA, The expression of adrenomedullin mRNA was examined by northern blot analysis of tissue from one of the tumo rs. Results: Immunoreactive adrenomedullin was detected in tumor tissu es of three ectopic ACTH secreting tumors (0.60-18.5 pmol/g wet weight ), Calcitonin gene-related peptide, neuropeptide Y, endothelin-1 and c orticotropin-releasing hormone were also detected in the tumor tissues . The tumor tissue concentrations of immunoreactive adrenomedullin wer e comparable to those of these four peptides, but much lower than thos e of ACTH. Northern blot analysis showed the expression of adrenomedul lin mRNA in one tumor from which sufficient tissue was available for s uch study, The plasma concentration of immunoreactive adrenomedullin w as increased in one patient (41.3 pmol/l, control 13.5 +/- 3.6 pmol/l, mean +/- S.D., n = 12). Conclusions: These results suggest that adren omedullin is produced by ectopic ACTH-secreting tumors, together with other neuropeptides, and raise the possibility that adrenomedullin is related to the pathophysiology of these tumors.