Intestinal osmoregulation of single component meals in neonatal piglets

The ability of the neonatal stomach and duodenum to modify the osmolality of hypotonic and hypertonic meals containing a single nutrient was studied in 3- to 5-day-old piglets. Test meals were administered through a gastrostomy and samples of gastric content and all proximal jejunal effluent were collected every 30 minutes for 2 hours. Hypotonic meals (149 mosm/L) and hypertonic meals (497 mosm/L) of glucose, crystalline amino acids, or lipids were used. Results were similar after all meals. There were significant changes in intragastric osmolality at each postprandial time period. However, osmolality never returned to basal levels. During duodenal transit there were further increases in osmolality after hypotonic meals and decreases after hypertonic meals but isotonic levels were never achieved. As a result, chyme of widely divergent osmolality entered the jejunum until late in the observation periods. Influx of sodium, potassium, and chloride were similar after all meals and were independent of original meal osmolality. These data indicate that, in awake, unstressed neonatal piglets, the stomach and duodenum are capable of effective but incomplete osmoregulation of hypotonic and hypertonic single component meals.