ASC system activity is altered by development of cell polarity in trophoblast from human placenta
- 1 July 1993
- journal article
- research article
- Published by American Physiological Society in American Journal of Physiology-Cell Physiology
- Vol. 265 (1), C212-C217
- https://doi.org/10.1152/ajpcell.1993.265.1.c212
Abstract
Pathways of neutral amino acid uptake were investigated in vitro during differentiation of primary cultures of trophoblast isolated from full-term human placentas and a clone (b30) of the BeWo cell line. Inhibition of initial alanine (0.1 microM) uptake by 2-(methylamino)isobutyric acid and unlabeled alanine revealed two Na(+)-dependent systems and one Na(+)-independent transporter. Characterization of these transporters, by selective inhibition, suggested system A, ASC, and L-like transporters. Concomitant with formation of microvillous membrane and syncytium, system ASC activity decreased from 16.1 +/- 2.8 pmol.mg DNA-1.min-1 at 24 h to 2.4 +/- 1.1 pmol.mg DNA-1.min-1 at 72 h. Na(+)-independent alanine uptake increased from 6.0 +/- 2.0 to 12.9 +/- 0.9 pmol.mg DNA-1.min-1 at 24 and 72 h, respectively. Similarly, alpha-(methylamino)isobutyric acid-insensitive, Na(+)-dependent activity in b30 cells (100 microM alanine) decreased from 6.5 +/- 1.6 to 1.2 +/- 1.2 nmol.mg DNA-1.min-1 for control and forskolin-treated cells, respectively. We conclude that membrane specialization accompanying fusion and differentiation of the cytotrophoblast to form syncytiotrophoblast results in a polarization of neutral amino acid transport systems.Keywords
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