RAT ADRENOMEDULLIN INDUCES A SELECTIVE ARTERIAL VASODILATION VIA CGRP(1) RECEPTORS IN THE DOUBLE-PERFUSED MESENTERIC BED OF THE RAT

The present work was undertaken to study the effect of rat adrenomedul lin (rADM (1-50) and its C-terminal fragment (11-50)) in the endotheli um-intact arterial and venous vasculatures of the rat perfused mesente ric bed. rADM (1-50) and the fragment rADM (11-50) (1-1000 pmol) induc ed a dose-dependent and endothelium-independent vasodilation on the ar terial mesenteric vasculature. However, both peptides were inactive on the venous side of this vascular bed. The CGRP(1) receptor antagonist , hCGRP(8-37) (1 mu M), markedly reduced the vasodilation caused by rA DM (1-50) in the arterial mesenteric vasculature. Thus, our results sh ow that rADM (1-50) and its C-terminal fragment rADM (11-50) share pro perties similar to those of hCGRP. The blocking effect of hCGRP(8-37) supports a role for CGRP(1) receptor activation by adrenomedullin in t his vascular preparation.