Dietary protein level and stage of development affect expression of an intestinal peptide transporter (cPepT1) in chickens

The objective of this study was to evaluate the effect of dietary protein intake and stage of development on chicken intestinal peptide transporter (cPepT1) mRNA abundance. Chicks were sampled at embryonic d 16 (e 16) until the day of hatch (d 0). After hatch, mixed sex Cobb chicks were randomly assigned to diets containing 12, 18, or 24% crude protein (CP). Intakes of the 18 and 24% CP-fed birds were restricted to that consumed by the 12% CP-fed birds. Chickens were sampled on d 0, 1, 3, 5, 7, 10, 14, 21, 28, and 35. The experiment was repeated with the addition of a 4th group with free access to the 24% CP diet. PepT1 mRNA abundance in the duodenum, jejunum, and ileum was quantified by Northern blot. PepT1 mRNA was barely detectable between e 16 and 20 but increased 14- to 50-fold by d 0 (P < 0.001). In chickens fed 12% CP, cPepT1 mRNA abundance decreased throughout the experiment, whereas those fed the restricted 18 or 24% CP diets showed an increase in cPepT1 mRNA abundance (protein X time interaction, P < 0.01). In chicks with free access to the 24% CP diet, cPepT1 mRNA decreased until d 14 but returned to an intermediate level at d 35 (protein X time interaction, P < 0.01). The relative abundance of cPepT1 mRNA varied among intestinal segments with greater abundance occurring in the duodenal or jejunal sections (P < 0.05). Our results indicate that expression of cPepT1 mRNA is regulated by both dietary protein intake and developmental stage.