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This Article Full Text Full Text (PDF) All Versions of this Article: jas.2007-0333v1 86/9/2321    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Regmi, P. R. Articles by Oba, M. PubMed PubMed Citation Articles by Regmi, P. R. Articles by Oba, M.

Effects of ammonia load on glucose metabolism by isolated ovine duodenal mucosa^1,2

Department of Agricultural Food and Nutritional Science, University of Alberta, Edmonton, Canada, T6G 2P5

³ Corresponding author: masahito.oba{at}ualberta.ca

To determine the effects of ammonia load on glucose metabolism in ruminant small intestinal tissues, duodenal mucosal cells (DMC) were isolated from growing female sheep (n = 10; 46. 0 ± 0. 8 kg of BW) fed diets differing in CP content: high (19. 4%) vs. low (13. 1%). Ammonia concentration in the duodenal digesta fluid was greater for sheep fed a high CP diet compared with those fed a low CP diet (16. 4 ± 1. 0 vs. 9. 1 ± 1. 8 mM). The isolated primary mucosal cells were incubated for 90 min with [2-¹³C] glucose (3 mM) and ammonium chloride (0, 0. 1, 1, 5, 10, 20, or 50 mM) in Krebs-Ringer HEPES buffer. It was hypothesized that DMC would increase glucose carbon utilization for the synthesis of nonessential AA when the ammonia concentration in the incubation media increased. However, utilization of glucose carbon for alanine synthesis decreased linearly (P = 0. 03) as the ammonia concentration in the incubation media increased. Furthermore, glucose disappearance and utilization of glucose carbon for aspartate synthesis were not affected (P > 0. 47) by the ammonia concentration. Contrarily, in vitro glucose disappearance was greater (P = 0. 03) for DMC isolated from sheep fed a low CP diet vs. a high CP diet [14. 6 ± 1. 6 vs. 8. 6 ± 1. 3 nmol·(10⁶ cells)^–1·(90 min) ^–1], and hexokinase activity was greater (P = 0. 01) in the mucosa of sheep fed a low CP diet compared with a high CP diet (1. 22 ± 0. 05 vs. 1. 04 ± 0. 02 mUnit/mg of protein). These observations indicate that ammonia load does not affect the extent of glucose utilization by DMC, and that glucose carbon may not play a significant role for the synthesis of alanine, aspartate, or glutamate when DMC are exposed to increased concentrations of ammonia.

Key Words: ammonia • duodenal mucosal cell • glucose • ovine • nonessential amino acid