NITRIC OXIDE INHIBITION IN AN OVINE MODEL OF HEART FAILURE

SUMMARY 1. The role of nitric oxide (NO) in congestive heart failure was investigated by studying the acute haemodynamic, hormonal and renal effects of NG‐monomethyl‐l‐arginine (l‐NMMA), a nitric oxide inhibitor, given as incremental bolus doses in six sheep before (normal) and after induction of heart failure (HF) by rapid left ventricular pacing (LVP). 2. l‐NMMA caused significant initial dose‐dependent rises in left ventricular systolic pressure, mean arterial pressure (MAP), peripheral resistance (PR) and left atrial pressure and declines in cardiac output in both normal and HF states (maximum response in 2–6 min). These responses were all but abolished when l‐arginine was given concurrently with l‐NMMA. The dose‐response curve for the l‐NMMA‐induced rise in MAP was shifted to the right following LVP (P