The effects of L-arginine administration on systemic hemodynamics and plasma concentrations of neuro-endocrine hormones and amino acids were investigated in 10 normotensive healthy volunteers. Nitrite/nitrate in urine and cyclic guanosine monophosphate (c-GMP) in plasma were also measured as indicators of release of nitric oxide (NO).
L-arginine administration (30g/300ml/30min) caused hypotension (mean arterial pressure; 79.3±3.9mmHg fell to 68.8±2.2mmHg) with tachycardia (62.3±2.3 beats/min increased to 67.5±1.9 beats/min). The plasma concentration of L-arginine before administration was 98.8±8.2μmol/l and increased to 7263±567 μmol/l 20min after administra-tion. Cardiac output also increased to 127.2±3.9% by L-arginine administration. Total peripheral resistance was calculated to fall to 65.9±2.0%. L-arginine administration slightly changed several hormones, but all values were within normal ranges. Nitrite/nitrate in urine increased 142.1±12.4% compared to the values before L-arginine administration. Plasma concentrations of c-GMP and L-citrulline, the by-product of NO from L-arginine, were also significantly increased by L-arginine administration.
All our results provide evidence for the first time that systemically administered L-arginine releases NO in man.