Vascular relaxing mechanism of denopamine in isolated canine coronary, femoral, mesenteric, and renal arteries

We investigated the mechanism of vascular relaxation produced by denopamine (deno), an oral positive inotropic agent that has selective β1-adrenergic action. Deno concentration-dependently (0.1 µM–30 µM) relaxed ring segments of canine femoral, mesenteric, and renal arteries which were partially precontracted with 1 µm phenylephrine or norepinephrine, but did not relax those precontracted with 5 µM prostaglandin F2α or 40 mM K+. The relaxation was not significantly inhibited by pretreatment with 10 µM propranolol or metoprolol. Deno produced a parallel rightward shift in concentration-response curves to phenylephrine in femoral and renal arteries. The Schild plot yielded linear regressions of slopes of 1.301 ± 0.106 and 0.823 ± 0.122, respectively, which were not significantly different from unity. The pA2 values of Deno against phenylephrine in femoral and renal arteries were 5.41 ± 0.03 and 5.76 ± 0.06, respectively.