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Journal of Animal Science Abstract - Animal Nutrition

Metabolic acidosis in sheep alters expression of renal and skeletal muscle amino acid enzymes and transporters1


This article in JAS

  1. Vol. 88 No. 2, p. 707-717
    Received: May 04, 2009
    Accepted: Oct 02, 2009
    Published: December 4, 2014

    2 Corresponding author(s):

  1. Y. Xue*,
  2. S. F. Liao*,
  3. K. W. Son*,
  4. S. L. Greenwood,
  5. B. W. McBride,
  6. J. A. Boling* and
  7. J. C. Matthews 2
  1. Department of Animal and Food Sciences, University of Kentucky, Lexington 40546; and
    Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario, Canada N1G 2W1



To determine the effect of metabolic acidosis on expression of l-Gln, l-Glu, and l-Asp metabolizing enzymes and transporters, the relative content of mRNA, protein, or mRNA and protein, of 6 enzymes and 5 transporters was determined by real-time reverse transcription-PCR and immunoblot analyses in homogenates of kidney, skeletal muscle, and liver of growing lambs fed a common diet supplemented with canola meal (control; n = 5) or HCl-treated canola meal (acidosis; n = 5). Acidotic sheep had a 790% greater (P = 0.050) expression of renal Na+-coupled neutral AA transporter 3 mRNA and a decreased expression of renal glutamine synthetase mRNA (47% reduction, P = 0.037) and protein (57% reduction, P = 0.015) than control sheep. No change in renal cytosolic phosphoenolpyruvate carboxykinase (protein and mRNA), glutaminase (mRNA), or l-Glu dehydrogenase (protein) was found. In skeletal muscle, acidotic sheep had 101% more (P = 0.026) aspartate transaminase protein than did control sheep, whereas no change in the content of 3 Na+-coupled neutral AA transporters (mRNA) or 2 high-affinity l-Glu transporter proteins was found. In liver, no change in the content of any assessed enzyme or transporter was found. Collectively, these findings suggest that tissue-level responses of sheep to metabolic acidosis are different than for nonruminants. More specifically, these results indicate the potential capacity for metabolism of l-Asp and l-Glu by skeletal muscle, and l-Gln absorption by kidneys, but no change in hepatic expression of l-Gln metabolism, elaborates previous metabolic studies by revealing molecular-level responses to metabolic acidosis in sheep. The reader is cautioned that the metabolic acidosis model employed in this study differs from the increased plasma lactate-induced metabolic acidosis commonly observed in ruminants fed a highly fermentable grain diet.

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