Characteristics of L-lactic acid transport in basal membrane vesicles of human placental syncytiotrophoblast.
The characteristics of L-lactic acid transport across the trophoblast basal membrane were investigated and compared with those across the brush-border membrane by using membrane vesicles isolated from human placenta. The uptake of L-[(14)C]lactic acid into basal membrane vesicles was Na(+) independent, and an uphill transport was observed in the presence of a pH gradient ([H(+)](out) > [H(+)](in)). L-[(14)C]lactic acid uptake exhibited saturation kinetics with a K(m) value of 5.89 +/- 0.68 mM in the presence of a pH gradient. p-Chloromercuribenzenesulfonate and alpha-cyano-4-hydroxycinnamate inhibited the initial uptake, whereas phloretin or 4,4'-diisothiocyanostilbene-2,2'-disulfonate did not. Mono- and dicarboxylic acids suppressed the initial uptake. In conclusion, L-lactic acid transport in the basal membrane is H(+) dependent and Na(+) independent, as is also the case for the brush-border membrane transport, and its characteristics resemble those of monocarboxylic acid transporters. However, there were several differences in the effects of inhibitors between basal and brush-border membrane vesicles, suggesting that the transporter(s) involved in L-lactic acid transport in the basal membrane of placental trophoblast may differ from those in the brush-border membrane.
Inuyama
Masako
M
Department of Medico-Pharmaceutical Sciences, Graduate School of Pharmaceutical Sciences, Higashi-ku, Fukuoka 812-8582, Japan.
Ushigome
Fumihiko
F
Emoto
Akiko
A
Koyabu
Noriko
N
Satoh
Shoji
S
Tsukimori
Kiyomi
K
Nakano
Hitoo
H
Ohtani
Hisakazu
H
Sawada
Yasufumi
Y
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D002731:4-Chloromercuribenzenesulfonate / Q000494:pharmacology; D001693:Biological Transport, Active / Q000187:drug effects / Q000502:physiology; D002250:Carbon Radioisotopes; D002264:Carboxylic Acids / Q000494:pharmacology; D002462:Cell Membrane / Q000737:chemistry* / Q000378:metabolism*; D002469:Cell Separation; D003373:Coumaric Acids / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D019344:Lactic Acid / Q000378:metabolism* / Q000493:pharmacokinetics; D008871:Microvilli / Q000737:chemistry / Q000378:metabolism; D027501:Monocarboxylic Acid Transporters / Q000378:metabolism; D010693:Phloretin / Q000494:pharmacology; D010920:Placenta / Q000166:cytology; D012964:Sodium / Q000378:metabolism; D013347:Subcellular Fractions / Q000737:chemistry / Q000378:metabolism; D014327:Trophoblasts / Q000737:chemistry* / Q000166:cytology
D002250:Carbon Radioisotopes; D002264:Carboxylic Acids; D003373:Coumaric Acids; D004791:Enzyme Inhibitors; D027501:Monocarboxylic Acid Transporters; C007175:alpha-cyano-4-hydroxycinnamate; D019344:Lactic Acid; D002731:4-Chloromercuribenzenesulfonate; D012964:Sodium; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D010693:Phloretin