Peripheral distribution and gene expression of adrenomedullin in the rat: possible source of blood adrenomedullin

Adrenomedullin (AM) was detected in all tissues examined with the highest concentrations in adrenal gland, lung and cardiac atrium. High concentrations of pre-proadrenomedullin mRNA were also detected in the lung, cardiac atrium, adrenal gland, thoracic aorta and mesenteric artery for the first time by solution-hybridization-RNase protection assay. The molecular forms of rat AM in various tissues and plasma were also characterized by Biogel P-30 gel filtration chromatography. We found no significant difference in immunoreactive AM levels between the veins draining the kidney, the lung and the adrenal and the systemic arterial blood. The very low peptide/mRNA ratio and the AM/precursor ratio in the mesenteric artery and thoracic aorta suggest that blood vessels may be the main source of plasma AM. (C) 2000 Harcourt Publishers Ltd.