Threonine utilization in the small intestine of the pig

Abstract

Since the intestine is one of the most metabolically active tissues in the body, a novel technique was developed to determine if threonine incorporation into protein in the small intestine of the pig varies as threonine levels are varied. We used the gut loop model and intraluminal flooding dose technique in anesthetized pigs to observe how varying luminal availability of threonine affects the amount of threonine that is incorporated into total protein and mucin in small intestinal mucosa. Three loops per pig (n=5) were isolated and a complete amino acid mixture containing 0, 75 or 200% of the threonine requirement of the gut was continuously perfused for 1.5 hours. Immediately following, an identical amino acid mixture containing a 3H-phenylalanine flooding dose was continuously circulated for an additional 0.5 hours. Following the perfusion, the tissue was removed and mucosa analyzed for threonine incorporation. Preliminary data from three pigs suggest that threonine incorporation rate was lower in the presence of deficient (0%: 55 ± 24 dpm/umol/min) and excess (200%: 59 ± 22 dpm/umol/min) luminal threonine compared to the adequate level (75%: 70 ± 23 dpm/umol/min). Threonine incorporation rate into mucin will also be presented. This model and technique can be used as a novel approach to measure the intestinal requirement for threonine. Future experiments will use this method to investigate the impact of gut stress on intestinal amino acid. (Supported by NSERC).