Ethanolamine transport in human placental brush-border membrane vesicles.
Pathways for transport of ethanolamine by human placental epithelia were investigated by measurement of [3H]ethanolamine uptake in brush-border membrane vesicles isolated by divalent cation precipitation. The presence of a conductive uptake pathway for ethanolamine was suggested by the marked stimulation of ethanolamine uptake to levels exceeding equilibrium induced by an inside-negative potassium diffusion potential. Evidence to suggest conductive ethanolamine uptake resulted from a mediated transport process included 1) the concentration-dependent inhibition by choline; 2) trans-stimulation of choline and ethanolamine uptake by ethanolamine; and 3) substrate-specific inhibition by chemically related analogs. Transport of both choline and ethanolamine by a common facilitated diffusion mechanism is suggested by 1) trans-stimulation of choline uptake by ethanolamine; 2) mutual inhibition of conductive choline and ethanolamine uptake by ethanolamine and choline; 3) the effect of ethanolamine on the kinetics of conductive choline uptake; and 4) the rank order inhibition of choline and ethanolamine uptake by the same panel of chemical analogs. The present study identifies the presence of a facilitated diffusion mechanism as a brush-border membrane transport pathway for choline and ethanolamine accumulation by human placenta.
Grassl
S M
SM
Department of Pharmacology, State University of New York Upstate Medical University, Syracuse, New York 13210, USA. grassls@upstate.edu
D000328:Adult; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002794:Choline / Q000378:metabolism; D004058:Diffusion; D004983:Ethanolamines / Q000378:metabolism*; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism*; D010920:Placenta / Q000187:drug effects / Q000378:metabolism*; D011247:Pregnancy; D013379:Substrate Specificity; D014475:Uncoupling Agents / Q000494:pharmacology
D004983:Ethanolamines; D014475:Uncoupling Agents; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D002794:Choline