Table 1.

Postprandial human blood-flow rates

Organ	Blood flow (L/min/70 kg)	Organ balance (M) (µm/min/70 kg; +, net output; −, net uptake)
		Urea	Glutamine	Alanine	Ammonia
GI tract	1.1 (FPV)	−61	−50	+21	+66
Liver	0.45 (FHA)	+305	+2.3	−82	−75
Kidney	1.24	−244	−30	+13	15
Brain	0.78	0	−20	0	0
Muscle	1	0	+97.67	+48	−6

Notes: In GI tract (portal vein), liver (hepatic artery), kidney, brain, and muscle and net organ balance M (+, production; −, uptake)27,48,98,164 of urea, glutamine, alanine, and NH₃.20–23 Urea organ balances are based on total nitrogen balance, assuming that 20% of the urea formed in the liver is metabolized by GI tract bacterial urease and the other 80% excreted in the kidney. The NH₃ balance for the kidney is from van de Poll et al,27 GI tract and liver from portal vein and hepatic vein measurements in patients with idiopathic portal hypertension from Nomura et al110 or during cholecystectomy from McDermott et al.111 Renal NH₃ balance refers to the net NH₃ added to the systemic circulation. An additional 32 µm/min/70 kg of NH₃ is produced in the kidney and excreted in the urine. Muscle balances are theoretical (not experimental) rates that have been adjusted to produce a steady state (total solute production = total solute uptake). Organ flow rates are from Levitt.43

Abbreviation: GI, gastrointestinal.