The effect of oral antioxidants on brachial artery flow-mediated dilation following 5 and 10 min of ischemia.
In light of the current methodological developments in flow-mediated dilation (FMD) testing and the recognition that oxidative stress may play an important role in regulating this process, the present study sought to: (1) compare flow-mediated dilation (FMD) following 5 and 10 min of forearm cuff occlusion, and (2) evaluate the role of oxidative stress on vasodilation, both distal and proximal to the cuff. Of the 14 subjects studied, 6 partook solely in a validation study of the antioxidant cocktail (AOC; vitamins C, E, and alpha-lipoic acid), while the remaining 8 subjects underwent FMD assessment in response to 5 and 10 min of forearm occlusion following ingestion of AOC or placebo. Although the efficacy of the AOC was clearly documented by elevated plasma ascorbate levels (approximately 95%) and a reduced free radical concentration (approximately 65%), no effects of acute oral antioxidants were observed. FMD was significantly augmented in response to 10 min of forearm occlusion when compared to 5 min, whether expressed as % change (10.1 +/- 2 vs. 4.5 +/- 1%, respectively) or absolute change in diameter (0.035 +/- 0.005 vs. 0.018 +/- 0.005 cm, respectively). Additionally, post-occlusion shear rate (28,640 +/- 2,799 vs. 18,629 +/- 1,724/s, AUC), FMD/shear rate (approximately 50%), and time to peak dilation (68 +/- 7 vs. 53 +/- 8 s) were greater following 10 min of occlusion. In contrast to previous studies, this investigation has identified a greater brachial artery FMD in response to 10 versus 5 min of forearm ischemia, which appears to be unexplained by oxidative stress.
Harris
Ryan A
RA
Georgia Prevention Institute, Medical College of Georgia, Augusta, GA 30912, USA. ryharris@mcg.edu
Nishiyama
Steven K
SK
Wray
D Walter
DW
Tedjasaputra
Vince
V
Bailey
Damian M
DM
Richardson
Russell S
RS
D000284:Administration, Oral; D000328:Adult; D000975:Antioxidants / Q000008:administration & dosage* / Q000494:pharmacology; D001205:Ascorbic Acid / Q000097:blood; D001916:Brachial Artery / Q000187:drug effects* / Q000502:physiology; D018592:Cross-Over Studies; D004311:Double-Blind Method; D006801:Humans; D006940:Hyperemia / Q000503:physiopathology; D007511:Ischemia / Q000503:physiopathology*; D008297:Male; D010919:Placebos; D012039:Regional Blood Flow / Q000187:drug effects*; D013997:Time Factors; D014664:Vasodilation / Q000187:drug effects* / Q000502:physiology; D055815:Young Adult
D000975:Antioxidants; D010919:Placebos; D001205:Ascorbic Acid