BIOAVAILABILITY OF NUCLEOSIDES IN INTESTINAL EXPLANTS OF NEONATAL PIGLETS

Abstract

29 In addition to free nucleotides, there are other sources of nucleosides present in human milk, such as ribonucleic acid (RNA), which may contribute to supply a significant amount of nucleosides to the infant intestine. To determine the current bioavailability of nucleosides to the intestinal epithelium, jejunal explants from 20 days old piglets were cultured in plates containing Williams medium supplemented with glutamine, insulin and antibiotics. Four different models were evaluated, with four replicates of explants for each one of the models. In the first model, the explants were cultured only with the medium mentioned above. In this model, there was a negative control which contained the medium without explant. In the second model, the medium was supplemented with RNA (60 mg/L). In this model, there was a positive control, with nuclease P1, and a negative control, without explant and enzyme. In the third model the medium was supplemented with nucleotides (50 mg/L); in this model there was also a positive control, with Bacterial Alkaline Phosphatase, and a negative one, without explant and enzyme. In the fourth model, the medium was supplemented with nucleosides (50 mg/L); in this model there was a negative control, which contained the medium with nucleosides but without any explant. Aliquots of medium were taken at different times (0, 2, 5, 15, 30, 60 and 180 minutes) and the nucleoside content was determined in the first and in the fourth model, and nucleoside and nucleotide contents were determined in the second and in the third models. Results obtained in the first model indicated that the concentration of nucleosides in the medium slightly increased during the period of culture, indicating that the explant is liberating a small amount of them to the medium. In the second model, the concentration of nucleotides and nucleosides increased during the period of cultured indicating that RNA was being hydrolyzed to nucleotides and these ones to nucleosides. In the third model, the concentration of nucleotides decreased whilst the concentration of nucleosides increased, suggesting the hydrolysis of the first ones to the second ones. Finally, in the fourth model, the initial concentration of nucleosides decreased, suggesting that the explant is consuming them. In conclusion, all these results suggest that RNA and free nucleotides present in human milk supply available nucleosides to the infant intestine, indicating that the current concentration of nucleotides used to supplement infant formulas in Europe should be reconsidered taken into account other sources present in human milk.