l-Arginine Transport across the Basal Plasma Membrane of the Syncytiotrophoblast of the Human Placenta from Normal and Preeclamptic Pregnancies

• Published in: The journal of clinical endocrinology and metabolism 2003-09, Vol.88 (9), p.4287-4292
• Main Authors: Speake, P. F., Glazier, J. D., Ayuk, P. T.-Y., Reade, M., Sibley, C. P., D’Souza, S. W.
• Format: Article
• Language: English
• Subjects: Adult; Alkaline Phosphatase - metabolism; Arginine - metabolism; Biological and medical sciences; Biological Transport, Active; Blotting, Western; Cationic Amino Acid Transporter 1 - biosynthesis; Cell Membrane - metabolism; Densitometry; Diseases of mother, fetus and pregnancy; Female; Gynecology. Andrology. Obstetrics; Humans; In Vitro Techniques; Kinetics; Medical sciences; Placenta - cytology; Placenta - metabolism; Pre-Eclampsia - metabolism; Pre-Eclampsia - pathology; Pregnancy; Pregnancy. Fetus. Placenta; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - biosynthesis; Trophoblasts - metabolism
• ISSN: 0021-972X; 1945-7197
• DOI: 10.1210/jc.2003-030067

Cord blood levels of nitrate/nitrite, as a measure of nitric oxide (NO), are generally increased in preeclampsia. As l-arginine is the precursor for NO synthesis, we hypothesized that l-arginine transport across the syncytiotrophoblast basal plasma membrane (BM) of placentas from preeclamptic patients is also increased. Glutamine-sensitive and -insensitive [3H]l-arginine uptakes into BM vesicles were measured and expressed as femtomoles per milligram of protein per minute. Total l-arginine uptake was 418 ± 15 (mean ± sem; n = 9) in BM from control placentas (CBM) and 495 ± 27 (n = 7) in BM from preeclamptic placentas (PE BM; P < 0.05, by two-tailed t test). Glutamine insensitive (system y+) uptake was 45 ± 3 (n = 6) in CBM, with a significantly higher uptake of 97 ± 23 (n = 5) into PE BM (P < 0.05, by two-tailed t test). There was no significant difference in glutamine-sensitive uptake between the two groups. The expression of mRNA for human cationic amino acid transporter (hCAT) 1, 2, and 4 (system y+ genes) and 4F2hc (heavy chain of system y+L) was not different in homogenates of whole placenta from the two groups. Western blotting data showed that hCAT-1 protein expression in PE BM was higher than that in CBM. These data suggest increased activity of the BM system y+ cationic amino acid transporter in preeclampsia. If reflected in vivo, a similar increase in transporter activity could alter the delivery of l-arginine to syncytiotrophoblast eNOS.