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Glutamine metabolism in ovine splanchnic tissues: effects of infusion of ammonium bicarbonate or amino acids into the abomasum

Published online by Cambridge University Press:  09 March 2007

R. Nieto ,
T. Obitsu ,
A. Fernández-Quintela ,
D. Bremner ,
E. Milne ,
A. G. Calder  and
G. E. Lobley
R. Nieto*
Affiliation:
Rowett Research Institute, Greenburn Road, Bucksburn, Aberdeen AB21 9SB, Scotland, UK
T. Obitsu
Affiliation:
Rowett Research Institute, Greenburn Road, Bucksburn, Aberdeen AB21 9SB, Scotland, UK
A. Fernández-Quintela
Affiliation:
Rowett Research Institute, Greenburn Road, Bucksburn, Aberdeen AB21 9SB, Scotland, UK
D. Bremner
Affiliation:
Rowett Research Institute, Greenburn Road, Bucksburn, Aberdeen AB21 9SB, Scotland, UK
E. Milne
Affiliation:
Rowett Research Institute, Greenburn Road, Bucksburn, Aberdeen AB21 9SB, Scotland, UK
A. G. Calder
Affiliation:
Rowett Research Institute, Greenburn Road, Bucksburn, Aberdeen AB21 9SB, Scotland, UK
G. E. Lobley
Affiliation:
Rowett Research Institute, Greenburn Road, Bucksburn, Aberdeen AB21 9SB, Scotland, UK
*
*Corresponding author: Dr Rosa Nieto, present address Unidad de Nutrición Animal, Estación Experimental del Zaidín C.S.I.C., Camino del Jueves, s/n 18100, Armilla (Granada), Spain, fax +34 958 572 753, email [email protected]
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Abstract

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This study investigates the effects of increased NH3 or amino acid supply on glutamine utilisation and production by the splanchnic tissues of fed sheep. Six sheep, prepared with vascular catheters in the aorta, mesenteric, portal and hepatic veins, were fed grass pellets to 1·1×energy maintenance requirements. Each treatment involved a 4 d abomasal infusion, of either ammonium bicarbonate (AMM; 23·4 μmol/kg0·75 per min), water (CONT), or a mixture of amino acids that excluded glutamine and glutamate (AA; 46·8 μmol amino acid-N/kg0·75 per min). The treatments simulated nutritional extremes in terms of the balance of absorbed N. Kinetics across the whole gut and the liver were monitored during an intra-jugular infusion of [5-15N]glutamine. Blood flow across the whole gut or liver were unaffected by treatment. Both AMM and AA infusions doubled the hepatic release of urea-N compared with CONT (P<0·02). AA infusion decreased arterial glutamine concentration by 26 % (P<0·01) and 23 % (P<0·05) compared with AMM and CONT respectively. Despite this, whole-body glutamine flux was not affected by treatment. In contrast, AMM infusion increased hepatic glutamine production by 40 % compared with CONT (P<0·02). This provided a mechanism to ensure NH3 supply to the periphery was maintained within the normal low physiological levels. Hepatic glutamine utilisation tended to increase during AA infusion, probably to ensure equal inflows of N to the ornithine cycle. Between 6 and 10 % of NH3 absorbed across the digestive tract was derived from the amido-N of glutamine. Overall, splanchnic glutamine utilisation accounted for 45–70 % of whole-body glutamine flux.

Keywords

Glutamine15N kineticsUreagenesisAmmoniaAmino acidsPortal-drained visceraLiverSheep
Type
Research Article
Information
British Journal of Nutrition , Volume 87 , Issue 4 , April 2002 , pp. 357 - 366
Copyright
Copyright © The Nutrition Society 2002

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