| Autor: |
Grassl, Steven M. |
| Zdroj: |
The Journal of Pharmacology and Experimental Therapeutics; August 2001, Vol. 298 Issue: 2 p695-702, 8p |
| Abstrakt: |
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. |
| Databáze: |
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