Unusual abundance of arginine and ornithine in porcine allantoic fluid

The concentrations of free arginine, ornithine, and glutamine in porcine allantoic and amniotic fluids were determined on Days 30,35, 40, and 45 of gestation. Arginine and ornithine were the most abundant amino acids in allantoic fluid on Days 35-40 and 45 of gestation, respectively. Arginine and ornithine nitrogen accounted for 40%, 50%, and 55% of the total free alpha-amino acid nitrogen in allantoic fluid on Days 35, 40, and 45 of gestation, respectively. Glutamine was the most abundant amino acid in amniotic fluid during early gestation and was also abundant in allantoic fluid. On Day 45 of gestation, glutamine nitrogen accounted for 41% of the total free alpha-amino acid nitrogen in amniotic fluid. The unusual abundance of arginine (2.5-4.1 mM) and ornithine (1.08-2.52 mM) in allantoic fluid on Days 35-40 of gestation has not been reported for any other biological fluid. These results are novel and interesting with respect to the role of these two basic amino acids in fetal-placental nutrition and metabolism.