Differences in potency of big endothelin-1-induced pressor action in rat isolated perfused mesenteric artery, hindquarter and lung.

We compared the pressor response to endothelin-1 (ET-1) with that of big endothelin-1 (big ET-1) in mesenteric arteries, hindquarters and lungs of rats. In these three preparations, both peptides caused a concentration-dependent increase in the perfusion pressure. The ratio of big ET-1 concentration to ET-1 concentration needed for causing the same pressor action is different between organs; i.e., a mesentery >> a hindquarter > or = a lung. Exposure to phosphoramidon, a metalloproteinase inhibitor, significantly suppressed the pressor response to big ET-1, in a similar fashion. This suppression is likely to be due to the inhibition of phosphoramidon-sensitive endothelin converting enzyme, since the inhibitor does not suppress an action of ET-1. Apparently there is a difference in potency for phosphoramidon-sensitive vasoconstriction of big ET-1 between organs and presumably regional differences in the functional phosphoramidon-sensitive conversion of big ET-1 in vasculatures.