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Stereospecificity of High‐and Low‐Affinity Transport of Choline Analogues into Rat Cortical Synaptosomes
Author(s) -
Ferguson S. S. G.,
Diksic M.,
Collier B.
Publication year - 1991
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1991.tb08238.x
Subject(s) - choline , stereoselectivity , chemistry , enantiomer , transporter , stereospecificity , stereochemistry , organic cation transport proteins , membrane transport , biochemistry , biophysics , membrane , biology , gene , catalysis
The present experiments used methylcholines to examine the stereoselectivity of choline transport into rat synaptosomes. R (+)‐α‐methylcholine and S (+)‐β‐methylcholine were significantly better inhibitors of the high‐affinity choline transport system than were their enantiomers. Although both enantiomers of α‐and of β‐methylcholine inhibited [ 3 H]choline transport, only R (+)‐α‐methylcholine and S (+)‐β‐methylcholine could be transported by the high‐affinity choline uptake mechanism. Therefore, we conclude that the chiral requirements for recognition of and for transport by the high‐affinity transporter are dearly different. In addition to high‐affinity choline transport, Na + ‐independent low‐affinity transport was measured. This process transported R (+)‐α‐methylcholine, but not S (‐)‐α‐methylcholine; however, it showed no stereoselectivity for the enantiomers of β ‐ methylcholine. Thus, high‐and low‐affinity choline transport mechanisms exhibit distinct differences in their substrate selectivities. We suggest that the stereoselective properties of choline transport might present a unique opportunity to study choline uptake and metabolism.