Placental lactate transporter activity and expression in intrauterine growth restriction.
OBJECTIVE
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 <.05). MCT1 and MCT4 were expressed in BM vesicles, but there was no difference in expression between the IUGR and AGA groups.


CONCLUSIONS
These findings suggest that in IUGR placental lactate transport capacity in the BM is reduced, which may adversely affect placental lactate clearance.
Settle
Paul
P
Division of Human Development, University of Manchester, St. Mary's Hospital, Manchester, United Kingdom.
Sibley
Colin P
CP
Doughty
Ian M
IM
Johnston
Tracey
T
Glazier
Jocelyn D
JD
Powell
Theresa L
TL
Jansson
Thomas
T
D'Souza
Stephen W
SW
D000653:Amniotic Fluid; D015153:Blotting, Western; D002250:Carbon Radioisotopes; D005260:Female; D005317:Fetal Growth Retardation / Q000378:metabolism*; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature; D019344:Lactic Acid / Q000378:metabolism*; D027501:Monocarboxylic Acid Transporters / Q000032:analysis / Q000235:genetics* / Q000378:metabolism*; D009124:Muscle Proteins / Q000032:analysis; D010920:Placenta / Q000737:chemistry* / Q000378:metabolism*; D011247:Pregnancy; D011522:Protons; D016216:Ultrasonography, Prenatal
D002250:Carbon Radioisotopes; D027501:Monocarboxylic Acid Transporters; D009124:Muscle Proteins; D011522:Protons; C406962:SLC16A4 protein, human; D019344:Lactic Acid