Comparative effects of adrenomedullin, an adrenomedullin analog, and CGRP in the pulmonary vascular bed of the cat and rat.

Responses to synthetic human adrenomedullin (ADM), a novel hypotensive peptide initially isolated from human pheochromocytoma cells, an ADM analog (ADM15-52), and a structurally related peptide, calcitonin gene-related peptide (CGRP), were compared in the pulmonary vascular bed of the cat and rat under constant flow conditions. When tone was increased with U46619, intraarterial injections of ADM (0.03-0.3 nmol), ADM15-52 (0.03-0.3 nmol), and of CGRP (0.03-0.3 nmol) caused dose-related decreases in pulmonary arterial perfusion pressure. When the relative vasodilator activity of the peptides was compared on a nmol basis, ADM was approximately 10-fold more potent in the cat than in the rat, whereas vasodilator responses to CGRP were very similar in both species. CGRP was slightly more potent than ADM in the rat, whereas ADM was slightly more potent than CGRP in the cat. ADM and ADM15-52 had similar pulmonary vasodilator activity in the cat, whereas the full sequence peptide was slightly more potent than ADM15-52 in the rat. The present data demonstrate that ADM has significant vasodilator activity in the pulmonary vascular beds of the cat and of the rat, and that the relative potency of the vasodilator effects of ADM and ADM15-52 are different in the two species.