COMPARISON OF RESPONSES TO ADRENOMEDULLIN AND ADRENOMEDULLIN ANALOGS IN THE MESENTERIC VASCULAR BED OF THE CAT

Responses to adrenomedullin, a newly discovered hypotensive peptide is olated from human pheochromocytoma cells, and the carboxy terminal 15- 52 (adrenomedullin-(15-52)) and 22-52 (adrenomedullin-(22-52)) amino a cid fragments of adrenomedullin were investigated in the mesenteric va scular bed of the cat. Under constant flow conditions, injections of a drenomedullin, adrenomedullin-(15-52), and calcitonin gene-related pep tide (CGRP) in doses of 0.003-1 nmol into the perfused superior mesent eric artery caused significant dose-related decreases in mesenteric ar terial perfusion pressure. Mesenteric vasodilator responses to adrenom edullin and adrenomedullin-(15-52) were similar in magnitude and durat ion, while vasodilator responses to CGRP were greater in magnitude and longer in duration than those produced by adrenomedullin or adrenomed ullin-(15-52) when these agents were injected in doses of 0.1-1 nmol. Adrenomedullin-(22-52) caused no significant change in mesenteric arte rial perfusion pressure when injected in doses up to 10 nmol. These re sults suggest that amino acids 15-52 and the six-membered ring structu re of adrenomedullin are important for the expression of vasodilator a ctivity in the mesenteric vascular bed of the cat.