Tissue distribution of a peptide transporter mRNA in sheep, dairy cows, pigs, and chickens.

A 446-bp cDNA fragment encoding a peptide transport protein was cloned from sheep omasum and used as a probe to study the distribution of the peptide transport protein mRNA in various tissues of sheep, dairy cows, pigs, and chickens. Because the predicted amino acid sequence of this fragment was 85.8, 90.5, and 90.5% identical to rabbit, human, and rat intestinal peptide transporter (PepT1), respectively, it is believed that this cloned fragment represents PepT1 from sheep. In sheep (n = 5) and lactating Holstein cows (n = 3), hybridization was observed with mRNA from the omasum, rumen, duodenum, jejunum, and ileum. The estimated size of mRNA was 2.8 kb. No hybridization was observed with mRNA from the abomasum, cecum, colon, liver, kidney, and semitendinosus and longissimus muscles of either species or the mammary gland of the dairy cows. In pigs (n = 6), the probe hybridized with mRNA from the duodenum, jejunum, and ileum. There was no hybridization with mRNA from the stomach, large intestine, liver, kidney, and semitendinosus and longissimus muscles. Two bands, 3.5 and 2.9 kb, were observed with northern blot analysis, indicating two RNA transcripts that may result from alternative mRNA processing. In White Leghorns (n = 15) and broilers (n = 20), the strongest hybridization was found in the duodenum, but the jejunum and ileum showed faint bands. The size of mRNA in chickens was 1.9 kb. Other tissues, including the crop, proventriculus, gizzard, ceca, liver, kidney, and muscles showed no hybridization to the probe. In conclusion, mRNA for PepT1 is present in the small intestine of all animals examined and the omasal and ruminal epithelium of sheep and dairy cows. The size of the mRNA varied among species.