Background: Intraluminal nutrients increase superior mesenteric artery
(SMA) blood Bow. Little is known about the effect of circulating nutr
ients. Methods: The effect of a commercially available mixed amino aci
ds solution, given either intravenously (IVAA) or intraduodenally (IDA
A), on SMA hemodynamics was investigated in five healthy volunteers (t
hree men, two women; 20-30 years old). Amino acids were given at a rat
e of 250 mg protein/kg/h for 2 h. Saline was used as control solution.
Doppler ultrasound measurements of SMA hemodynamics were performed af
ter 0, 30, 60, and 120 min. Results: IVAA had no significant effect on
SMA hemodynamics. In contrast, IDAA significantly (P < 0.05) increase
d SMA flow volume by 60-80% over basal and the IVAA experiment. This i
ncrease in SMA flow volume during IDAA resulted primarily from a signi
ficant (P < 0.05) increase in time-averaged velocity. During IDAA both
the peak systolic velocity and the end-diastolic velocity increased s
ignificantly (P < 0.05). Conclusions: In healthy subjects intraduodena
l, but not intravenous, amino acids significantly increase SMA blood f
low.