Journal of Animal Science, Vol 79, Issue 5 1329-1336, Copyright © 2001 by American Society of Animal Science

JOURNAL ARTICLE

Molecular identification of high-affinity glutamate transporters in sheep and cattle forestomach, intestine, liver, kidney, and pancreas

J. A. Howell, A. D. Matthews, K. C. Swanson, D. L. Harmon and J. C. Matthews
Department of Animal Sciences, University of Kentucky, Lexington 40546-0215, USA.

Glutamate metabolism is essential to support many facets of metabolism. The objective of this study was to determine the tissue distribution of glutamate transporters known to support the tissue metabolism of glutamate. The expression of proteins capable of high-affinity glutamate transport (system X-(AG)) by epithelia isolated from the rumen, omasum, duodenum, jejunum, ileum, cecum, and colon and homogenates of liver, kidney, and pancreatic tissues from wethers (n = 4; BW = 28.4 +/- 8.4 kg) and steers (n = 3; BW = 426 +/- 32.3 kg) fed forage-based diets was evaluated by immunoblot analysis. Proteins EAAC1 (62, 93 kDa) and GLT-1 (142, 188, >202 kDa) were expressed by every tissue examined. In contrast, GLAST1 (140 kDa) was expressed only by the pancreas, and EAAT4 (67 kDa) was detected only in sheep brain. To corroborate protein expression data, the presence and size of transporter mRNA in ileal, liver, and pancreatic homogenates were evaluated by Northern analysis. GLAST1 mRNA (2.4, 4.3 kb) was detected only in the pancreas, whereas EAAC1 (2.2, 2.8 kb) and GLT-1 (12.1 kb) mRNA transcripts were detected in all three tissues. The expression of EAAT4 and GLT-1 mRNA was confirmed by reverse transcriptase-polymerase chain reaction analyses. Sequencing of the resulting partial-length ovine GLT-1 cDNA revealed 100% identity with the rat homolog. Overall, these data demonstrate that sheep and cattle share the same pattern of system X-(AG) transporter expression, which differed among tissues and transporter isoforms. Accordingly, these data provide the fundamental knowledge to initiate research that determines whether the expression of high-affinity glutamate transporters by ruminants is sensitive to ontogenic and(or) dietary regulation.

This article has been cited by other articles:

				S. F. Liao, E. S. Vanzant, D. L. Harmon, K. R. McLeod, J. A. Boling, and J. C. Matthews Ruminal and abomasal starch hydrolysate infusions selectively decrease the expression of cationic amino acid transporter mRNA by small intestinal epithelia of forage-fed beef steers J Dairy Sci, March 1, 2009; 92(3): 1124 - 1135. [Abstract] [Full Text] [PDF]

				K. R. Brown, G. A. Anderson, K. Son, G. Rentfrow, L. P. Bush, J. L. Klotz, J. R. Strickland, J. A. Boling, and J. C. Matthews Growing steers grazing high versus low endophyte (Neotyphodium coenophialum)-infected tall fescue have reduced serum enzymes, increased hepatic glucogenic enzymes, and reduced liver and carcass mass J Anim Sci, February 1, 2009; 87(2): 748 - 760. [Abstract] [Full Text] [PDF]

				S. F. Liao, M. J. Alman, E. S. Vanzant, E. D. Miles, D. L. Harmon, K. R. McLeod, J. A. Boling, and J. C. Matthews Basal Expression of Nucleoside Transporter mRNA Differs Among Small Intestinal Epithelia of Beef Steers and Is Differentially Altered by Ruminal or Abomasal Infusion of Starch Hydrolysate J Dairy Sci, April 1, 2008; 91(4): 1570 - 1584. [Abstract] [Full Text] [PDF]

				S. F. Liao, E. S. Vanzant, J. A. Boling, and J. C. Matthews Identification and expression pattern of cationic amino acid transporter-1 mRNA in small intestinal epithelia of Angus steers at four production stages J Anim Sci, March 1, 2008; 86(3): 620 - 631. [Abstract] [Full Text] [PDF]

				M. Z. Fan, J. C. Matthews, N. M. P. Etienne, B. Stoll, D. Lackeyram, and D. G. Burrin Expression of apical membrane L-glutamate transporters in neonatal porcine epithelial cells along the small intestinal crypt-villus axis Am J Physiol Gastrointest Liver Physiol, August 1, 2004; 287(2): G385 - G398. [Abstract] [Full Text] [PDF]

				A. N. Scheaffer, J. S. Caton, M. L. Bauer, D. A. Redmer, and L. P. Reynolds The effect of pregnancy on visceral growth and energy use in beef heifers J Anim Sci, July 1, 2003; 81(7): 1853 - 1861. [Abstract] [Full Text] [PDF]

				J. A. Howell, A. D. Matthews, T. C. Welbourne, and J. C. Matthews Content of ileal EAAC1 and hepatic GLT-1 high-affinity glutamate transporters is increased in growing vs. nongrowing lambs, paralleling increased tissue D- and L-glutamate, plasma glutamine, and alanine concentrations J Anim Sci, April 1, 2003; 81(4): 1030 - 1039. [Abstract] [Full Text] [PDF]

				K. C. Swanson, J. C. Matthews, C. A. Woods, and D. L. Harmon Postruminal Administration of Partially Hydrolyzed Starch and Casein Influences Pancreatic {alpha}-Amylase Expression in Calves J. Nutr., March 1, 2002; 132(3): 376 - 381. [Abstract] [Full Text] [PDF]