Effect of amino acids on mesenteric blood flow in humans

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