Abstract
ABSTRACT: Carrier-mediated β-D-hydroxybutyrate transport in brush-border membrane (maternal-sided) vesicles prepared from trophoblast rat placenta was studied. The existence of a carrier-mediated transport system for β-D-hydroxybutyrate in brush-border membrane vesicles was substantiated by the strong inhibitory effect of the protein modifier p-chloromercuriphenyl sulfonic acid and by the saturability of β-D-hydroxybutyrate uptake as a function of β-D-hydroxybutyrate concentration. β-D-hydroxybutyrate uptake was stimulated by the presence of an inward-directed proton gradient but not by an inward-directed Na+ gradient. The mechanism for transport of β-D-hydroxybutyrate seems to be a β-D-hydroxybutyrate/H+ symport and not a β-D-hydroxybutyrate/OH− antiport because β-D-hydroxybutyrate transport was not sensitive to 4,4-diisothiocyano-2,2‘-stilbenedisulfonic acid or furosemide. The Km, Vmax, and kd calculated by applying the iteration procedure to the data were 16 mM, 58 nmol. mg−1.10 s−1, and 0 nL.mg−1-s−1, respectively. The β-D-hydroxybutyrate transport system might be shared by other monocarboxylic acids, and the carrier shows reversibility and exchange properties. There were no significant changes in the kinetic parameters of the β-D-hydroxybutyrate transport system during the last 3 d of gestation. Nevertheless, there was a significant increase in the capacity of the β-D-hydroxybutyrate transport system in brush-border membrane vesicles prepared from fasted pregnant rats, suggesting that the rise in maternal ketone body levels occurring as a consequence of maternal starvation is concurrent with the stimulation of the activity of the β-D-hydroxybutyrate placental carrier to supply the fetus with ketone bodies. The signal mediating the stimulation of carrier activity due to starvation remains to be elucidated.
Similar content being viewed by others
Article PDF
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
de la Torre, S., Serrano, M. & Medina, J. Carrier-Mediated β-D-Hydroxybutyrate Transport in Brush-Border Membrane Vesicles from Rat Placenta. Pediatr Res 32, 317–323 (1992). https://doi.org/10.1203/00006450-199209000-00014
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1203/00006450-199209000-00014