Affiliation:
1. Department of Obstetrics and Gynecology, Erasmus University, Rotterdam, The Netherlands 3000 DR; and
2. Division of Perinatal Medicine, Departments of Pediatrics, Pharmacology and Physiology, University of Colorado Health Sciences Center, Denver, Colorado 80262
Abstract
Uterine and umbilical uptakes of alanine (Ala) were measured in 10 ewes before (control) and during intravenous infusion of Ala, which increased maternal arterial Ala concentration from 115 ± 14 to 629 ± 78 μM ( P < 0.001). In 8 of these ewes, placental Ala fluxes were traced by constant intravenous infusion ofl-[3,3,3-2H3]Ala in the mother andl-[1-13C]Ala in the fetus. Rates are reported as micromoles per minute per kilogram fetus. Ala infusion increased uterine uptake (2.5 ± 0.6 to 15.6 ± 3.1, P < 0.001), umbilical uptake (3.1 ± 0.5 to 6.9 ± 0.8, P < 0.001), and net uteroplacental utilization (−0.7 ± 0.8 to 8.6 ± 2.7, P < 0.01) of Ala. Control Ala flux to fetus from mother ( R f,m) was much less than the Ala flux to fetus from placenta ( R f,p) (0.17 ± 0.04 vs. 5.0 ± 0.6). Two additional studies utilizingl-[U-13C]Ala as the maternal tracer confirmed the small relative contribution of R f,m to R f,p. During maternal Ala infusion, R f,m increased significantly ( P < 0.02) but remained a small fraction of R f,p (0.71 ± 0.2 vs. 7.3 ± 1.3). We conclude that maternal Ala entering the placenta is metabolized and exchanged for placental Ala, so that most of the Ala delivered to the fetus is produced within the placenta. An increase in maternal Ala concentration increases placental Ala utilization and the fetal uptake of both maternal and placental Ala.
Publisher
American Physiological Society
Subject
Physiology (medical),Physiology,Endocrinology, Diabetes and Metabolism
Cited by
20 articles.
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