Nitrogen movements in the upper jejunum lumen in humans fed low amounts of casein or beta-lactoglobulin
Mahé, S.; Benamouzig, R.; Gaudichon, C.; Huneau, J.F.; De Cruz, I.; Rautureau, J.; Tomé, D.
Gastroenterologie Clinique et Biologique 19(1): 20-26
1995
ISSN/ISBN: 0399-8320 PMID: 7720985 Document Number: 1090
Objectives and methods: To compare the progression of milk proteins in the upper part of the digestive tract, gastro-jejunal nitrogen movements were studied in 6 healthy human volunteers after beta-lactoglobulin and casein ingestion. 400 mL of water (control), purified beta-lactoglobulin (20 g/L) or casein (20 g/L), each adjusted to 25 mu-Ci with 14C-polyethylene glycol, were given per os. Samples were collected in the stomach and 20 cm below the Treitz ligament every 20 min for 2 hours and measured for volume, osmolarity, ions and nitrogen content. Results: The jejunal flow rate peaked in the 0-20 min period following water and beta-lactoglobulin ingestion, and in the 20-40 min period after casein ingestion. The gastric half-emptying time (T-1/2 min) of the liquid phase was significantly different (P lt 0.05) for water (12.1 +- 0.8), beta-lactoglobulin (14.5 +- 3.3) and casein (26.5 +- 9.3). Before ingestion of the test meals, the basal rate of nitrogen was 9.14 +- 4.09 mmol/h in the jejunum. The total nitrogen content in the jejunum peaked significantly in the 0-20 min period after beta-lactoglobulin ingestion and the 20-40 min period after casein ingestion. The apparent gastro-jejunal protein absorption values were 63 % for casein and 66% for beta-lactoglobulin in the 120 min period. Conclusions: These results show that beta-lactoglobulin and casein behave differently in the upper part of the digestive tract due to different gastric emptying rates.
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