[Adrenomedullin under physiologic and pathologic conditions]

Adrenomedullin (AM) is a novel 52-aminoacid-peptide hormone, originally isolated from human phaeocromocytoma. Adrenomedullin acts as a local autocrine and/or paracrine vasoactive hormone and has vasodilator and blood lowering properties, but its exact role is still uncertain. Adrenomedullin is considered to play an important endocrine role in various tissues maintaining the electrolyte and fluid homeostasis. Its normal plasma concentration is low. In hypertension, chronic renal failure and congestive heart failure its plasma concentration increases parallel to the seriousness of the disease. It is assumed that this peptide may be important under pathologic conditions compensating the effects of the vasoconstrictor molecules. Till now, investigations have proved that in diabetic angiopathies the levels and the production of vasoconstrictor factors and adrenomedullin were increased, while, those of other relaxing substances including nitrogenoxid were decreased. It is still uncertain whether increased release of adrenomedullin in diabetes is a compensatory mechanism or a coincidental event. Although, the precise role of adrenomedullin in the pathogenesis of diabetic complications is still to be elucidated, the elevated concentration of adrenomedullin in diabetes--which influences the vascular functions--let us speculate that there might be a certain interaction between adrenomedullin induction and vascular functions in diabetes. Thus, the induction of vascular adrenomedullin could be a new target of a therapeutic approach to the diabetic complications.