Dietary Arginine Supplementation Enhances Placental Water Transport and Angiogenesis in Gestating Gilts

This study was conducted to test the hypothesis that dietary supplementation with 0.4% L-arginine between days 14 and 30 of gestation would enhance survival and development of conceptuses (embryo and its extra-embryonic membranes) in gilts. Gilts were bred at the onset of second estrus and fed twice daily 1 kg of a corn- and soybean meal-based diet containing 12% crude protein beginning on day 0 of gestation (the day of breeding). Either 0.4% L-arginine or an isonitrogenous amount of L-alanine (control) was supplemented to the basal diet from days 14 to 30 of gestation. At day 30 of gestation, gilts were hysterectomized and euthanized to obtain uteri, conceptuses and fetal fluids. Placental water transport was determined by using Ussing chambers. Concentrations of AAs in fetal fluids and maternal plasma were determined by HPLC. Total RNA and protein were extracted from the frozen tissues. Quantitative RT-PCR and western blotting were performed to determine the changes in gene expression at mRNA and protein levels. Porcine trophectoderm (PTr2) cells were cultured in medium with different concentrations of arginine to determine water transport and cGMP production. Compared to the control group, arginine supplementation increased (P < 0.05) embryonic survival from 87.3% in the control group to 96.5% in the arginine group. Allantoic fluid volume was increased by 25% and amniotic fluid volume was increased by 48% in the arginine group. The placentae of arginine-supplemented gilts were more vascularized in terms of the number and size of blood vessels. Compared to the control group, arginine supplementation increased (P < 0.05) the number of placental blood vessels; placental expression of angiogenic factors VEGFA120, VEGFR1, VEGFR2, eNOS, PlGF, GTP-CH and FGF-2; and placental transport of water. We conclude that dietary arginine supplementation to pigs between days 14 and 30 of gestation improves survival and development of the conceptuses through stimulating placental water transport and angiogenesis