The action of a dopamine (DA1) receptor agonist, fenoldopam in human vasculature in vivo and in vitro.

Human subjects (for in vivo forearm blood flow measurement) and isolated rings of human blood vessels including renal, mesenteric, and lumbar arteries, and saphenous vein (for in vitro studies)

Fenoldopam (intra-arterial administration in vivo; concentration-dependent application in vitro)

Baseline/preconstricted state, and co-administration with antagonists ((R) sulpiride, metoclopramide, guanethidine, SCH 23390)

Forearm blood flow (in vivo) and vascular relaxation (in vitro)surrogate