Potent vasodilator responses to human urotensin-II in human pulmonary and abdominal resistance arteries

Abstract

The peptide human urotensin-II (hUT-II) and its receptor have recently been cloned. The vascular function of this peptide in humans, however, has yet to be determined. Vasoconstrictor and vasodilator responses to hUT-II were investigated in human small muscular pulmonary arteries [∼170 μm internal diameter (ID)] and human abdominal resistance arteries (∼200 μm ID). Vasodilator responses were investigated in endothelin-1 (3 nM) precontracted vessels and, in the small pulmonary vessels, compared with the known vasodilators adrenomedullin, sodium nitroprusside, and acetylcholine. In human small pulmonary arteries, hUT-II did not induce vasoconstriction but was a potent vasodilator [−log M concentration causing 50% of the maximum vasodilator effect (pIC₅₀) 10.4 ± 0.5; percentage of reduction in tone ( E _max) 81 ± 8% (vs. 23 ± 11% in time controls), n = 5]. The order of potency for vasodilation was human urotensin-II = adrenomedullin (pIC₅₀ 10.1 ± 0.4, n = 6) > sodium nitroprusside (pIC₅₀ 7.4 ± 0.2, n = 6) = acetylcholine (pIC₅₀ 6.8 ± 0.3, n = 6). In human abdominal arteries, hUT-II did not induce vasoconstriction but was a potent vasodilator [pIC₅₀ 10.3 ± 0.7; E _max96 ± 8% (vs. 43 ± 16% in time controls), n = 4]. This is the first report that hUT-II is a potent vasodilator but not a vasoconstrictor of human small pulmonary arteries and systemic resistance arteries.