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This Article Full Text Full Text (PDF) All Versions of this Article: 286/3/E376    most recent 00428.2003v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via ISI Web of Science (6) Citing Articles via Google Scholar Google Scholar Articles by Józwik, M. Articles by Battaglia, F. C. Search for Related Content PubMed PubMed Citation Articles by Józwik, M. Articles by Battaglia, F. C.

Reciprocal inhibition of umbilical uptake within groups of amino acids

Maciej Jówik,¹ Cecilia Teng,² Randall B. Wilkening,² Giacomo Meschia,² and Frederick C. Battaglia²

¹Department of Gynecology, Medical University of Bialystok, 15-276 Bialystok, Poland; and ²Division of Perinatal Medicine, Department of Pediatrics, University of Colorado Health Sciences Center, Aurora, Colorado 80010

Submitted 23 September 2003 ; accepted in final form 7 November 2003

Eight pregnant sheep were infused with two amino acid mixtures of different composition: essential amino acids only and the essentials plus some of the nonessentials. Uterine and umbilical uptakes of amino acids were measured before and during infusion. For most of the amino acids, the infusion increased both maternal plasma concentration and umbilical uptake. However, depending on the infusate composition, the increase in maternal concentration of some amino acids was associated with no change or a significant reduction in umbilical uptake. Data were pooled from this and other, similar studies to test the hypothesis that umbilical uptake of several amino acids can be inhibited by coinfused amino acids. The test consisted of fitting the data, by means of multiple regression analysis, to the linear transformation of a saturation kinetics equation in which uptake is assumed to depend on maternal arterial concentrations. The analysis showed significant inhibitory effects within the neutral essential amino acids group and within the lysine-arginine group, with no demonstrable interaction between the two groups. Uterine uptakes did not show clear evidence of saturability and inhibitory interactions, suggesting a large transport capacity and low transporter affinity on the maternal surface of the trophoblast. We conclude that the transport of any given amino acid from placenta to fetus is a function of both its own maternal concentration and the maternal concentration of inhibitory amino acids.

cationic amino acids; essential amino acids; neutral amino acids; placental transport