Abstract
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.
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This study was supported by National Institutes of Health grants HD-30367 and MO1-RR-00056. Meredith Snook Parrott was supported by a Clinical Scientist Training Program scholarship from the University of Pittsburgh School of Medicine.
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Parrott, M.S., von Versen-Hoeynck, F., Ness, R.B. et al. System A Amino Acid Transporter Activity in Term Placenta Is Substrate Specific and Inversely Related to Amino Acid Concentration. Reprod. Sci. 14, 687–693 (2007). https://doi.org/10.1177/1933719107306895
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DOI: https://doi.org/10.1177/1933719107306895