ASSOCIATION BETWEEN THE ACTIVITY OF THE SYSTEM-A AMINO-ACID TRANSPORTER IN THE MICROVILLOUS PLASMA-MEMBRANE OF THE HUMAN PLACENTA AND SEVERITY OF FETAL COMPROMISE IN INTRAUTERINE GROWTH RESTRICTION

Primarily, our objectives were to compare system A amino acid transpor ter activity in the microvillous plasma membrane (MVM) of placentas fr om normally grown (appropriate for gestational age, AGA) and intrauter ine growth-restricted (IUGR) fetuses delivered during the third trimes ter, as a whole and in relation to the severity of IUGR, Ten AGA and 1 6 IUGR pregnancies were studied at the time of elective cesarean secti on performed between 28: and 40 wk of gestation, Severity of IUGR preg nancies was assessed primarily by Doppler velocimetry and fetal heart rate monitoring, Placental MVM vesicles were prepared, and system A ac tivity in these was measured, The transporter activity was significant ly lower in IUGR compared with AGA pregnancies. Within the IUGR group system A activity was only significantly lower, compared with AGA, in cases that presented with a reduction in umbilical blood flow. We conc lude that placental MVM system A activity is lower in IUGR compared wi th AGA pregnancies delivered during the third trimester, System A acti vity is related to the severity of IUGR.