Coronary spasm can be induced by acetylcholine (ACh) ACh casues vasodilation when the endothelium is intact by releasing nitric oxide (NO). The aim of this study was to investigate whether L-arginine, the precursor of NO, could preserve endothelium-dependent vasodilation in patients with coronary artery spasm.

NO precusor L-arginine (20mg/kg/min) was infused intravenous for 30 minutes in nineteen patients with coronary spastic angina. Coronary spasm of the epicardial coronary artery (>75%) was induced by intracoronary injection of acetylcholine in incremental doses (ACh: A1 20ug, A2 50ug, A3 100ug) the spasm was then documented angiographically in all patients with coronary spastic angina. After the administration of L-arginine, intracoronary injection of acetylcholine was repeated as the same method in all coronary spastic angina patients.

After systemic infusion of L-arginine, the constrictor response to ACh was significanfly attenuated : no spastic response in 8 cases (42%), increased doses of ACh for provoking spasm in 8 cases (42%) and no change in 3 cases (16%). There were no significant change in blood pressure and heart rate after the administration of L-arginine.

The fact that L-arginine attenuated vasospasm provoked by ACh in human coronary arteries, suggests the possibilities that L-arginine may be used in the prevention and treatment of coronary spasm.