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Research Article Free access | 10.1172/JCI117386

Altered activity of the system A amino acid transporter in microvillous membrane vesicles from placentas of macrosomic babies born to diabetic women.

A G Kuruvilla, S W D'Souza, J D Glazier, D Mahendran, M J Maresh, and C P Sibley

Department of Child Health, University of Manchester, St. Mary's Hospital, United Kingdom.

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Department of Child Health, University of Manchester, St. Mary's Hospital, United Kingdom.

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Department of Child Health, University of Manchester, St. Mary's Hospital, United Kingdom.

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Department of Child Health, University of Manchester, St. Mary's Hospital, United Kingdom.

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Department of Child Health, University of Manchester, St. Mary's Hospital, United Kingdom.

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Department of Child Health, University of Manchester, St. Mary's Hospital, United Kingdom.

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First published August 1, 1994 - More info

Published in Volume 94, Issue 2 on August 1, 1994
J Clin Invest. 1994;94(2):689–695. https://doi.org/10.1172/JCI117386.
© 1994 The American Society for Clinical Investigation
First published August 1, 1994 - Version history
Abstract

Fetal macrosomia (FM) is a well-recognized complication of diabetic pregnancy but it is not known whether placental transport mechanisms are altered. We therefore studied the activity of the system A amino acid transporter, the system L amino acid transporter, and the Na+/H+ exchanger in microvillous membrane vesicles from placentas of macrosomic babies born to diabetic women (FM group), from placentas of appropriately grown babies born to diabetic women (appropriate for gestational age group) and from placentas of appropriately grown babies of normal women (control group). Sodium-dependent uptake of [14C]-methylaminoisobutyric acid at 30 s (initial rate, a measure of system A activity) was 49% lower into FM vesicles than into control vesicles (P < 0.02); this effect was due to a decrease in Vmax of the transporter with no change in Km. There was no significant difference in system A activity between the appropriate for gestational age group and control or FM group. There was also no difference between system L transporter or Na+/H+ exchanger activity between the three groups. We conclude that the number of system A transporters per milligram of membrane protein in the placental microvillous membrane is selectively reduced in diabetic pregnancies associated with FM.

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