Reproductive Sciences

 

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Reproductive Sciences, Vol. 14, No. 7, 687-693 (2007)
DOI: 10.1177/1933719107306895

System A Amino Acid Transporter Activity in Term Placenta Is Substrate Specific and Inversely Related to Amino Acid Concentration

Meredith Snook Parrott, BS

Magee-Womens Research Institute University of Pittsburgh , Pittsburgh, Pennsylania, Department of Obstetrics and Gynecology and Reproductive Sciences University of Pittsburgh, Pittsburgh, Pennsylania, parrott.meredith{at}medstudent.pitt.edu

Frauke von Versen-Hoeynck, MD

Magee-Womens Research Institute University of Pittsburgh , Pittsburgh, Pennsylania, Department of Obstetrics and Gynecology and Reproductive Sciences University of Pittsburgh, Pittsburgh, Pennsylania

Roberta B. Ness, MD, MPH

Department of Epidemiology University of Pittsburgh, Pittsburgh, Pennsylvania

Nina Markovic, PhD

Department of Epidemiology University of Pittsburgh, Pittsburgh, Pennsylvania

James M. Roberts, MD

Magee-Womens Research Institute University of Pittsburgh , Pittsburgh, Pennsylania, Department of Epidemiology University of Pittsburgh, Pittsburgh, Pennsylvania, Department of Obstetrics and Gynecology and Reproductive Sciences University of Pittsburgh, Pittsburgh, Pennsylania

Using intact villous fragments from normal term placentas, the authors characterize the e fect of reduced amino acid availability on amino acid uptake via the system A amino acid transporter. Villous fragments deprived of amino acids demonstrate increased system A activity compared with those incubated in an amino acid—su ficient medium (P < .05). Similarly, placental villous fragments exposed to media containing only amino acids not specifically transported by system A have a significant increase in system A activity compared with villous fragments incubated in an amino acid—su ficient medium containing only substrates of system A (P < .05). There is a significant trend for increasing system A activity as the concentrations of the system A amino acid substrates are decreased (P < .01). Collectively, these data indicate that normal placentas can increase system A amino acid transporter activity in a substrate-specific and dose-dependent manner as a means to ensure optimal fetal growth in the presence of amino acid limitation.

Key Words: Placental villous fragments • amino acid uptake regulation • system A • amino acid starvation.


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