Hahn, Eugenia L.

β-Adrenergic hyporesponsiveness in congestive heart failure (CHF) is mediated, in part, by nitric oxide (NO). NO and brain natriuretic peptide (BNP) share cGMP as a second messenger. Left ventricular (LV) function and inotropic response to intravenous dobutamine (Dob) were assessed during sequential intracoronary infusion of saline, HS-142-1 (a BNP receptor antagonist), and HS-142-1 + NG-monomethyl-l-arginine (l-NMMA) in anesthetized dogs with CHF due to rapid pacing and in normal dogs during intracoronary infusion of saline, exogenous BNP, and sodium nitroprusside (SNP). In CHF dogs, intracoronary HS-142-1 did not alter the inotropic response to Dob [percent change in first derivative of LV pressure (%ΔdP/d t) 47 ± 4% saline vs. 54 ± 7% HS-142-1, P = not significant]. Addition of intracoronary l-NMMA to HS-142-1 enhanced the response to Dob (%ΔdP/d t 73 ± 8% l-NMMA + HS-142-1, P < 0.05 vs. H142-1). In normal dogs, intracoronary SNP blunted the inotropic response to Dob (%ΔdP/d t 93 ± 6% saline vs. 71 ± 5% SNP, P < 0.05), whereas intracoronary BNP had no effect. In CHF dogs, the time constant of LV pressure decay during isovolumic relaxation increased with intracoronary HS-142-1 (48 ± 4 ms saline vs. 58 ± 5 ms HS-142-1, P < 0.05) and further increased with intracoronary l-NMMA (56 ± 6 ms HS-142-1 vs. 66 ± 7 ms l-NMMA + HS-142-1, P < 0.05). Endogenous BNP and NO preserve diastolic function in CHF, whereas NO but not BNP inhibits β-adrenergic responsiveness.