L-arginine infusion increases basal but not activated cerebral blood flow in humans.
Nitric oxide is a potent vasodilator. Infusion of its precursor, L-arginine, results in increased cerebral blood flow (CBF) in experimental animals. We examined the effects of L-arginine infusion on CBF in humans using positron emission tomography and the quantitative H2(15)O method. Six subjects received 500 ml of 0.9% NaCl solution, and six subjects received an infusion of L-arginine (16.7 mg/kg/min; 500 mg/kg). Before and after the i.v. infusion, paired CBF measurements were performed at baseline and with vibrotactile stimulation of the right hand. In scans performed without vibrotactile stimulation, mean whole-brain CBF increased from 34.9 +/- 3.7 ml 100 g-1 min-1 to 38.2 +/- 4.4 ml 100 g-1 min-1. (9.5%; p < 0.005) after L-arginine infusion. The temporal pattern of CBF changes differed from that of plasma growth hormone and insulin levels and of arterial pH. In contrast, in the saline group, mean whole-brain CBF did not change significantly (35.8 +/- 5.9 ml 100 g-1 min-1 to 35.9 +/- 6.4 ml 100 g-1 min-1; 0.3%). Vibrotactile stimulation produced significant focal increases in CBF, which were unaffected by L-arginine infusion. L-arginine infusion was associated with an increase in plasma L-citrulline, a byproduct of nitric oxide synthesis.
Reutens
D C
DC
Positron Imaging Laboratories, McConnell Brain Imaging Centre, Montreal Neurological Institute, Canada.
McHugh
M D
MD
Toussaint
P J
PJ
Evans
A C
AC
Gjedde
A
A
Meyer
E
E
Stewart
D J
DJ
D000328:Adult; D001120:Arginine / Q000097:blood / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects; D002245:Carbon Dioxide / Q000097:blood; D002560:Cerebrovascular Circulation / Q000187:drug effects*; D002956:Citrulline / Q000097:blood; D017666:Deuterium Oxide; D005260:Female; D019382:Human Growth Hormone / Q000097:blood; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007328:Insulin / Q000097:blood; D008297:Male; D009569:Nitric Oxide / Q000502:physiology; D010313:Partial Pressure; D013268:Stimulation, Chemical; D013382:Subtraction Technique; D014055:Tomography, Emission-Computed; D014110:Touch / Q000502:physiology; D014665:Vasodilator Agents / Q000494:pharmacology*; D014732:Vibration
D007328:Insulin; D014665:Vasodilator Agents; D019382:Human Growth Hormone; D002245:Carbon Dioxide; D002956:Citrulline; D009569:Nitric Oxide; D001120:Arginine; D017666:Deuterium Oxide