Equine placenta expresses glutamine synthetase

Abstract

In most mammalian species the developing fetus utilizes large amounts of glutamine derived both from the maternal circulation and synthesized de novo in the placenta. The present study was designed to determine the role of the placenta in glutamine synthesis in the horse. The placentae from eight Standardbred mares were sampled immediately after parturition together with additional tissues obtained at necropsy from three Standbred mares during diestrous. Glutamine synthetase protein was detectable in the non-pregnant horn of the placenta in amounts similar to those seen in gluteus muscle, but the amount in the pregnant horn was two times greater than in the non-pregnant horn. Glutamine was the second most abundant amino acid in amniotic fluid at a concentration of 310 +/- 26 micromole/L with that of glycine being 535 +/- 48 micromole/L. The most abundant amino acids in placental tissue were glycine (3,732 +/- 194 micromole/Kg), glutamate (3,500 +/- 343 micromole/Kg) and glutamine (2,836 +/- 208 micromole/Kg). The results illustrate the importance of glutamine to the equine fetus and establish that the placenta, particularly the pregnant horn, has considerable capacity for glutamine synthesis.

Glutamine supplementation in a child with inherited GS deficiency improves the clinical status and partially corrects the peripheral and central amino acid imbalance

“…This observed neurodegeneration is consistent with experimental findings supporting the role of GS for Schwann cell differentiation [42]. During pregnancy, there is a great need for glutamine for normal ontogeny and brain development [43,44] and there is GS-dependent de novo synthesis of glutamine in the placenta [45]. As the glutamine transporters on the placenta are also upregulated to transport glutamine actively from the maternal circulation to the fetus the demand may be partially met by increased extraction of glutamine from the maternal circulation [46].…”

Uterine Gene Expression in the Live-Bearing Lizard, Chalcides ocellatus, Reveals Convergence of Squamate Reptile and Mammalian Pregnancy Mechanisms

“…One highly upregulated metabolic gene of particular note is glutamate–ammonia ligase (GLUL, also called glutamine synthetase). Glutamine is critical for the synthesis of nucleic acids and sugars as well as cell growth and differentiation (Self et al 2004), and upregulation of GLUL mirrors the pattern in numerous mammal species where glutamine concentrations in the fetal plasma are far higher than those in the maternal circulation (e.g., Wu et al 1995; Cetin 2001; Kwon et al 2003; Manso Filho et al 2009). Thus, the upregulation of GLUL is probably critical to maintaining both reptilian and mammalian pregnancies.…”

Placental metabolism: substrate requirements and the response to stress

“…In addition to oxidation, 6% of the glutamate taken up by the ovine placenta is converted to glutamine, which is then released into the foetal circulation in amounts exceeding its uterine uptake (Moores et al., ). Glutamine is also synthesized from BCAA and glutamate by the porcine and equine placenta (Manso Filho, Costa, Wu, McKeever, & Watford, ; Self et al., ). It is used for foeto‐placental synthesis of protein and glycosaminoglycans and is re‐converted back to glutamate by foetal ovine liver (Battaglia, ; Kim et al., ).…”