Placental Lactate Transporter Activity and Expression in Intrauterine Growth Restriction

Objectives: To compare lactate uptake in the microvillous plasma membrane (maternal facing [MVM]) in term and preterm placentas in intrauterine growth restriction (IUGR) and appropriate weight for gestational age (AGA) controls, and in the basal plasma membrane (fetal facing [BM]) at term. In addition, we examine the expression of monocarboxylate transporters (MCT1 and MCT4). Methods: We measured [14C] l-lactate uptakes into vesicles prepared from MVM and BM, stimulated by an inwardly directed H+ gradient. MCT expression was examined by Western blotting. Results: In term placentas, mean (± SE) [14C] l-lactate uptake into MVM vesicles of the IUGR (n = 6) and AGA (n = 11) groups at initial rate was similar (15.4 ± 2.3 versus 15.0 ± 1.1 pmol/mg protein/20 s). In preterm placentas, in IUGR (n = 3) and AGA (n = 3) groups, [14C] l-lactate uptake into MVM was also not significantly different. In BM vesicles from term placentas, [14C] l-lactate uptake was significantly lower in IUGR (n = 5) than in AGA (n = 6) controls (3.6 ± 0.4 versus 5.6 ± 0.6 pmol/mg protein/20 s, P